diff --git a/app/src/infrastructure/plc_communication_service.cpp b/app/src/infrastructure/plc_communication_service.cpp
index 386ad0c..8009b99 100644
--- a/app/src/infrastructure/plc_communication_service.cpp
+++ b/app/src/infrastructure/plc_communication_service.cpp
@@ -28,6 +28,32 @@ QModbusDataUnit::RegisterType registerType(RegisterArea area)
         ? QModbusDataUnit::Coils : QModbusDataUnit::HoldingRegisters;
 }
 
+QString modbusErrorText(QModbusDevice::Error error)
+{
+    switch (error)
+    {
+    case QModbusDevice::ReadError:
+        return QStringLiteral("读取 PLC 数据失败");
+    case QModbusDevice::WriteError:
+        return QStringLiteral("写入 PLC 数据失败");
+    case QModbusDevice::ConnectionError:
+        return QStringLiteral("PLC 串口连接失败");
+    case QModbusDevice::ConfigurationError:
+        return QStringLiteral("PLC 串口参数配置错误");
+    case QModbusDevice::TimeoutError:
+        return QStringLiteral("PLC 通信超时，请检查站号、串口参数和 RS-485 接线");
+    case QModbusDevice::ProtocolError:
+        return QStringLiteral("PLC 返回了无效或异常的 Modbus 响应");
+    case QModbusDevice::ReplyAbortedError:
+        return QStringLiteral("PLC 通信请求已取消");
+    case QModbusDevice::UnknownError:
+        return QStringLiteral("PLC 通信发生未知错误");
+    case QModbusDevice::NoError:
+    default:
+        return QStringLiteral("PLC 通信失败");
+    }
+}
+
 } // namespace
 
 PlcCommunicationService::PlcCommunicationService(
@@ -73,7 +99,7 @@ PlcCommunicationService::PlcCommunicationService(
             {
                 if (error != QModbusDevice::NoError)
                 {
-                    setError(master_->errorString());
+                    setError(modbusErrorText(error));
                 }
             });
 }
@@ -86,13 +112,14 @@ PlcCommunicationResult PlcCommunicationService::connectDevice(
     if (QString::fromStdString(configuration.portName).trimmed().isEmpty()
         || configuration.serverAddress < 1 || configuration.serverAddress > 247)
     {
-        return {false, "serial port and Modbus server address are required"};
+        return {false, "必须填写串口端口，并将 PLC 站号设置为 1~247"};
     }
     if (master_->state() != QModbusDevice::UnconnectedState)
     {
-        return {false, "PLC connection is already active"};
+        return {false, "PLC 连接已经启动，请先断开当前连接"};
     }
     configuration_ = configuration;
+    last_error_.clear();
     master_->setConnectionParameter(
         QModbusDevice::SerialPortNameParameter,
         QString::fromStdString(configuration.portName));
@@ -117,12 +144,12 @@ PlcCommunicationResult PlcCommunicationService::connectDevice(
         initial_read_changed_callback_(false);
     }
     rebuildPollBlocks();
+    setState(PlcConnectionState::Connecting);
     if (!master_->connectDevice())
     {
-        setError(master_->errorString());
+        setError(modbusErrorText(master_->error()));
         return {false, last_error_};
     }
-    setState(PlcConnectionState::Connecting);
     return {true, {}};
 }
 
@@ -240,7 +267,7 @@ void PlcCommunicationService::pollNextBlock()
     QModbusReply *reply = master_->sendReadRequest(request, configuration_.serverAddress);
     if (reply == nullptr)
     {
-        setError(master_->errorString());
+        setError(modbusErrorText(master_->error()));
         return;
     }
     pending_reply_ = reply;
@@ -284,7 +311,7 @@ void PlcCommunicationService::handleReadFinished(QModbusReply *reply, PollBlock
     }
     if (reply->error() != QModbusDevice::NoError)
     {
-        setError(reply->errorString());
+        setError(modbusErrorText(reply->error()));
         return;
     }
     const QModbusDataUnit result = reply->result();
@@ -320,7 +347,7 @@ RegisterWriteResult PlcCommunicationService::sendBitWrite(
     QModbusReply *reply = master_->sendWriteRequest(unit, configuration_.serverAddress);
     if (reply == nullptr)
     {
-        setError(master_->errorString());
+        setError(modbusErrorText(master_->error()));
         return {false, RegisterError::WriteRejected};
     }
     connect(reply, &QModbusReply::finished,
@@ -329,7 +356,7 @@ RegisterWriteResult PlcCommunicationService::sendBitWrite(
             {
                 if (reply->error() != QModbusDevice::NoError)
                 {
-                    setError(reply->errorString());
+                    setError(modbusErrorText(reply->error()));
                 }
                 reply->deleteLater();
             });
@@ -348,7 +375,7 @@ RegisterWriteResult PlcCommunicationService::sendWordWrite(
     QModbusReply *reply = master_->sendWriteRequest(unit, configuration_.serverAddress);
     if (reply == nullptr)
     {
-        setError(master_->errorString());
+        setError(modbusErrorText(master_->error()));
         return {false, RegisterError::WriteRejected};
     }
     connect(reply, &QModbusReply::finished,
@@ -357,7 +384,7 @@ RegisterWriteResult PlcCommunicationService::sendWordWrite(
             {
                 if (reply->error() != QModbusDevice::NoError)
                 {
-                    setError(reply->errorString());
+                    setError(modbusErrorText(reply->error()));
                 }
                 reply->deleteLater();
             });
diff --git a/app/src/ui/main_window.cpp b/app/src/ui/main_window.cpp
index a1397bb..73aac9a 100644
--- a/app/src/ui/main_window.cpp
+++ b/app/src/ui/main_window.cpp
@@ -100,6 +100,29 @@ QString fromUtf8(const std::string &value)
     return QString::fromUtf8(value.data(), static_cast<int>(value.size()));
 }
 
+QString plcStatusText(const RuntimeModeService &service)
+{
+    switch (service.plcConnectionState())
+    {
+    case PlcConnectionState::Connecting:
+        return MainWindow::tr("PLC 正在连接");
+    case PlcConnectionState::Connected:
+        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::Faulted:
+    {
+        const QString error = fromUtf8(service.plcError());
+        return error.isEmpty()
+            ? MainWindow::tr("PLC 通信故障")
+            : MainWindow::tr("PLC 通信故障：%1").arg(error);
+    }
+    case PlcConnectionState::Disconnected:
+    default:
+        return MainWindow::tr("PLC 已断开");
+    }
+}
+
 QString controlTypeText(HmiControlType type)
 {
     switch (type)
@@ -157,7 +180,7 @@ MainWindow::MainWindow(
         {
             QMetaObject::invokeMethod(
                 this,
-                [this] { updateModeUi(tr("PLC 通信状态已更新")); },
+                [this] { updateModeUi(plcStatusText(runtime_mode_service_)); },
                 Qt::QueuedConnection);
         });
     hmi_editor_service_.ensureDefaultPage();
@@ -1011,6 +1034,10 @@ void MainWindow::requestMode(ApplicationMode requested_mode)
     {
         restoreCurrentModeAction();
         QString message = transitionErrorText(result.error);
+        if (result.error == ModeTransitionError::InitialPlcReadRequired)
+        {
+            message += tr("；当前状态：%1").arg(plcStatusText(runtime_mode_service_));
+        }
         if (result.error == ModeTransitionError::SimulationStartFailed)
         {
             const LogicScanResult &error = runtime_mode_service_.simulationError();
@@ -1083,12 +1110,20 @@ void MainWindow::updateModeUi(const QString &message)
     ui_->configurePlcAction->setEnabled(
         policy.allowsProjectEditing && plc_state == PlcConnectionState::Disconnected);
     ui_->disconnectPlcAction->setEnabled(plc_state != PlcConnectionState::Disconnected);
-    if (plc_state == PlcConnectionState::Connected)
+    if (plc_state == PlcConnectionState::Connecting)
+    {
+        register_status_label_->setText(tr("PLC：正在连接"));
+    }
+    else if (plc_state == PlcConnectionState::Connected)
     {
         register_status_label_->setText(
             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::Faulted)
+    {
+        register_status_label_->setText(tr("PLC：通信故障"));
+    }
     updateSimulationUi(false);
     statusBar()->showMessage(message, 4000);
     ui_->outputList->addItem(message);