diff --git a/app/src/infrastructure/plc_communication_service.cpp b/app/src/infrastructure/plc_communication_service.cpp
index dd300f1..c84743f 100644
--- a/app/src/infrastructure/plc_communication_service.cpp
+++ b/app/src/infrastructure/plc_communication_service.cpp
@@ -16,6 +16,7 @@
 namespace {
 
 constexpr int kMaximumReadCount = 120;
+constexpr int kRecoveryProbeIntervalMs = 2000;
 
 std::string toUtf8(const QString &value)
 {
@@ -29,6 +30,18 @@ QModbusDataUnit::RegisterType registerType(RegisterArea area)
         ? QModbusDataUnit::Coils : QModbusDataUnit::HoldingRegisters;
 }
 
+bool isRecoverableTimeout(PlcCommunicationError error)
+{
+    return error == PlcCommunicationError::PlcNotResponding
+        || error == PlcCommunicationError::CommunicationTimeout;
+}
+
+bool isReadingState(PlcConnectionState state)
+{
+    return state == PlcConnectionState::Connected
+        || state == PlcConnectionState::Recovering;
+}
+
 } // namespace
 
 PlcCommunicationService::PlcCommunicationService(
@@ -48,6 +61,12 @@ PlcCommunicationService::PlcCommunicationService(
             return sendWordWrite(address, value);
         });
     connect(&poll_timer_, &QTimer::timeout, this, &PlcCommunicationService::pollNextBlock);
+    recovery_timer_.setSingleShot(true);
+    connect(
+        &recovery_timer_,
+        &QTimer::timeout,
+        this,
+        &PlcCommunicationService::probeRecovery);
     connect(master_.get(), &QModbusClient::stateChanged,
             this,
             [this](QModbusDevice::State device_state)
@@ -268,7 +287,7 @@ void PlcCommunicationService::applyPollAddresses(
     rebuildPollBlocks();
     poll_update_pending_ = false;
     pending_poll_addresses_.clear();
-    if (state_ == PlcConnectionState::Connected && pending_reply_ == nullptr)
+    if (isReadingState(state_) && pending_reply_ == nullptr)
     {
         pollNextBlock();
     }
@@ -276,7 +295,7 @@ void PlcCommunicationService::applyPollAddresses(
 
 void PlcCommunicationService::pollNextBlock()
 {
-    if (state_ != PlcConnectionState::Connected
+    if (!isReadingState(state_)
         || pending_reply_ != nullptr || poll_blocks_.empty())
     {
         return;
@@ -304,7 +323,7 @@ void PlcCommunicationService::pollNextBlock()
                     return;
                 }
                 handleReadFinished(reply, block);
-                if (state_ == PlcConnectionState::Connected
+                if (isReadingState(state_)
                     && reply->error() == QModbusDevice::NoError
                     && !poll_update_pending_
                     && block_index < initial_blocks_read_.size())
@@ -317,6 +336,10 @@ void PlcCommunicationService::pollNextBlock()
                     if (completed && !initial_read_completed_)
                     {
                         updateInitialReadCompleted(true);
+                        if (state_ == PlcConnectionState::Recovering)
+                        {
+                            setState(PlcConnectionState::Connected);
+                        }
                     }
                 }
                 if (pending_reply_ == reply)
@@ -332,9 +355,104 @@ void PlcCommunicationService::pollNextBlock()
             });
 }
 
+void PlcCommunicationService::probeRecovery()
+{
+    if (state_ != PlcConnectionState::Faulted
+        || !isRecoverableTimeout(last_error_type_))
+    {
+        return;
+    }
+    if (master_->state() != QModbusDevice::ConnectedState)
+    {
+        return;
+    }
+    if (pending_reply_ != nullptr)
+    {
+        recovery_timer_.start(kRecoveryProbeIntervalMs);
+        return;
+    }
+    if (poll_blocks_.empty())
+    {
+        return;
+    }
+    const PollBlock block = poll_blocks_.front();
+    const QModbusDataUnit request(
+        registerType(block.area), block.startAddress, 1);
+    QModbusReply *reply = master_->sendReadRequest(request, configuration_.serverAddress);
+    if (reply == nullptr)
+    {
+        handleRecoveryProbeFailure(master_->error());
+        return;
+    }
+    pending_reply_ = reply;
+    const std::uint64_t generation = connection_generation_;
+    connect(reply, &QModbusReply::finished,
+            this,
+            [this, reply, generation]
+            {
+                if (generation != connection_generation_)
+                {
+                    reply->deleteLater();
+                    return;
+                }
+                if (pending_reply_ == reply)
+                {
+                    pending_reply_ = nullptr;
+                }
+                const QModbusDevice::Error error = reply->error();
+                reply->deleteLater();
+                if (poll_update_pending_)
+                {
+                    const std::vector<RegisterAddress> addresses = pending_poll_addresses_;
+                    applyPollAddresses(addresses);
+                }
+                if (state_ != PlcConnectionState::Faulted
+                    || !isRecoverableTimeout(last_error_type_))
+                {
+                    return;
+                }
+                if (error != QModbusDevice::NoError)
+                {
+                    handleRecoveryProbeFailure(error);
+                    return;
+                }
+                restoreCommunication();
+            });
+}
+
+void PlcCommunicationService::handleRecoveryProbeFailure(QModbusDevice::Error error)
+{
+    if (state_ != PlcConnectionState::Faulted
+        || !isRecoverableTimeout(last_error_type_))
+    {
+        return;
+    }
+    if (error == QModbusDevice::ConnectionError)
+    {
+        const PlcCommunicationErrorContext context{
+            QString::fromStdString(configuration_.portName),
+            serial_session_opened_,
+            received_valid_response_};
+        setError(classifyPlcCommunicationError(error, context));
+        return;
+    }
+    recovery_timer_.start(kRecoveryProbeIntervalMs);
+}
+
+void PlcCommunicationService::restoreCommunication()
+{
+    received_valid_response_ = true;
+    last_error_type_ = PlcCommunicationError::None;
+    last_error_.clear();
+    rebuildPollBlocks();
+    setState(PlcConnectionState::Recovering);
+    poll_timer_.start(configuration_.pollIntervalMs);
+    pollNextBlock();
+}
+
 void PlcCommunicationService::handleReadFinished(QModbusReply *reply, PollBlock block)
 {
-    if (state_ != PlcConnectionState::Connected)
+    if (!isReadingState(state_))
     {
         return;
     }
@@ -481,6 +599,7 @@ void PlcCommunicationService::closeSerialSession()
     ++connection_generation_;
     disconnecting_ = true;
     poll_timer_.stop();
+    recovery_timer_.stop();
     pending_reply_ = nullptr;
     poll_update_pending_ = false;
     pending_poll_addresses_.clear();
@@ -512,6 +631,7 @@ void PlcCommunicationService::setError(const PlcCommunicationFailure &failure)
     last_error_type_ = failure.type;
     last_error_ = toUtf8(failure.message);
     poll_timer_.stop();
+    recovery_timer_.stop();
     updateInitialReadCompleted(false);
     const bool disconnected = failure.type == PlcCommunicationError::SerialPortOpenFailed
         || failure.type == PlcCommunicationError::SerialConnectionLost
@@ -527,4 +647,9 @@ void PlcCommunicationService::setError(const PlcCommunicationFailure &failure)
     {
         error_reported_callback_(last_error_);
     }
+    if (isRecoverableTimeout(failure.type)
+        && master_->state() == QModbusDevice::ConnectedState)
+    {
+        recovery_timer_.start(kRecoveryProbeIntervalMs);
+    }
 }
diff --git a/app/src/infrastructure/plc_communication_service.h b/app/src/infrastructure/plc_communication_service.h
index 7432cac..1afa37d 100644
--- a/app/src/infrastructure/plc_communication_service.h
+++ b/app/src/infrastructure/plc_communication_service.h
@@ -60,6 +60,9 @@ private:
     void rebuildPollBlocks();
     void applyPollAddresses(const std::vector<RegisterAddress> &addresses);
     void pollNextBlock();
+    void probeRecovery();
+    void handleRecoveryProbeFailure(QModbusDevice::Error error);
+    void restoreCommunication();
     void handleReadFinished(QModbusReply *reply, PollBlock block);
     RegisterWriteResult sendBitWrite(const RegisterAddress &address, bool value);
     RegisterWriteResult sendWordWrite(
@@ -74,6 +77,7 @@ private:
     PlcRegisterRepository &repository_;
     std::unique_ptr<QModbusRtuSerialMaster> master_;
     QTimer poll_timer_;
+    QTimer recovery_timer_;
     PlcSerialConfiguration configuration_;
     std::vector<RegisterAddress> poll_addresses_;
     std::vector<RegisterAddress> pending_poll_addresses_;
diff --git a/app/src/services/plc_communication_gateway.h b/app/src/services/plc_communication_gateway.h
index db4682c..37c0d45 100644
--- a/app/src/services/plc_communication_gateway.h
+++ b/app/src/services/plc_communication_gateway.h
@@ -24,6 +24,7 @@ enum class PlcConnectionState
     Disconnected,
     Connecting,
     Connected,
+    Recovering,
     Faulted
 };
 
diff --git a/app/src/ui/main_window.cpp b/app/src/ui/main_window.cpp
index 1ea9fdc..9988d00 100644
--- a/app/src/ui/main_window.cpp
+++ b/app/src/ui/main_window.cpp
@@ -113,6 +113,8 @@ QString plcStatusText(const RuntimeModeService &service)
         return service.initialPlcReadCompleted()
             ? MainWindow::tr("PLC 已连接，首次读取完成")
             : MainWindow::tr("PLC 已连接，正在读取工程使用的 M/D 地址");
+    case PlcConnectionState::Recovering:
+        return MainWindow::tr("PLC 通信已恢复，正在重新读取工程使用的 M/D 地址");
     case PlcConnectionState::Faulted:
     {
         const QString error = fromUtf8(service.plcError());
@@ -1243,6 +1245,10 @@ void MainWindow::updateModeUi(const QString &message)
             runtime_mode_service_.initialPlcReadCompleted()
                 ? tr("PLC：已连接，首读完成") : tr("PLC：已连接，正在首读"));
     }
+    else if (plc_state == PlcConnectionState::Recovering)
+    {
+        register_status_label_->setText(tr("PLC：通信已恢复，正在重新首读"));
+    }
     else if (plc_state == PlcConnectionState::Faulted)
     {
         register_status_label_->setText(tr("PLC：通信故障"));
diff --git a/app/tests/main_window_tests.cpp b/app/tests/main_window_tests.cpp
index 796b937..443758c 100644
--- a/app/tests/main_window_tests.cpp
+++ b/app/tests/main_window_tests.cpp
@@ -163,12 +163,54 @@ public:
     void completeInitialRead()
     {
         initial_read = true;
+        last_error_type = PlcCommunicationError::None;
+        last_error.clear();
+        if (connection_state == PlcConnectionState::Recovering)
+        {
+            connection_state = PlcConnectionState::Connected;
+            if (state_changed)
+            {
+                state_changed();
+            }
+        }
         if (initial_read_changed)
         {
             initial_read_changed(true);
         }
     }
 
+    void timeoutCommunication(const std::string &message)
+    {
+        initial_read = false;
+        last_error_type = PlcCommunicationError::CommunicationTimeout;
+        last_error = message;
+        connection_state = PlcConnectionState::Faulted;
+        if (initial_read_changed)
+        {
+            initial_read_changed(false);
+        }
+        if (state_changed)
+        {
+            state_changed();
+        }
+        if (error_reported)
+        {
+            error_reported(last_error);
+        }
+    }
+
+    void recoverCommunication()
+    {
+        initial_read = false;
+        last_error_type = PlcCommunicationError::None;
+        last_error.clear();
+        connection_state = PlcConnectionState::Recovering;
+        if (state_changed)
+        {
+            state_changed();
+        }
+    }
+
     void loseSerialConnection(const std::string &message)
     {
         initial_read = false;
@@ -683,6 +725,36 @@ void testOnlineWorkspaceShowsHmiAndFreeMonitorOnly()
     QAction *configure_action = requiredChild<QAction>(window, "configurePlcAction");
     QAction *disconnect_action = requiredChild<QAction>(window, "disconnectPlcAction");
     QListWidget *output = requiredChild<QListWidget>(window, "outputList");
+    gateway.timeoutCommunication(
+        "PLC 通信超时，本地串口 COM9 仍处于打开状态；请检查 PLC 供电和 RS-485 接线");
+    QApplication::processEvents();
+
+    require(mode_service.mode() == ApplicationMode::Editing,
+            "a PLC timeout must return online running to editing");
+    require(disconnect_action->isEnabled(),
+            "a timeout must keep disconnect available while the local port remains open");
+    require(configure_action->isEnabled()
+                && configure_action->text() == QStringLiteral("PLC 重新配置"),
+            "a timeout must keep PLC reconfiguration available");
+
+    gateway.recoverCommunication();
+    QApplication::processEvents();
+    require(mode_service.mode() == ApplicationMode::Editing,
+            "automatic communication recovery must remain in editing mode");
+    require(output->count() > 0
+                && output->item(output->count() - 1)->text().contains(
+                    QStringLiteral("通信已恢复")),
+            "automatic recovery must be retained in the output log");
+    online_action->trigger();
+    require(mode_service.mode() == ApplicationMode::Editing,
+            "recovered communication must complete a fresh initial read before online mode");
+
+    gateway.completeInitialRead();
+    QApplication::processEvents();
+    online_action->trigger();
+    require(mode_service.mode() == ApplicationMode::OnlineRunning,
+            "users must be able to re-enter online mode after the recovered initial read");
+
     gateway.loseSerialConnection(
         "PLC 串口 COM9 连接已中断；请检查 USB 转串口是否被拔出或已经失效");
     QApplication::processEvents();