diff --git a/frontend/src/api/simulation.js b/frontend/src/api/simulation.js
index 907911a..33efca0 100644
--- a/frontend/src/api/simulation.js
+++ b/frontend/src/api/simulation.js
@@ -152,3 +152,19 @@ export const getSimulationActions = (simulationId, params = {}) => {
   return service.get(`/api/simulation/${simulationId}/actions`, { params })
 }
 
+/**
+ * 关闭模拟环境（优雅退出）
+ * @param {Object} data - { simulation_id, timeout? }
+ */
+export const closeSimulationEnv = (data) => {
+  return service.post('/api/simulation/close-env', data)
+}
+
+/**
+ * 获取模拟环境状态
+ * @param {Object} data - { simulation_id }
+ */
+export const getEnvStatus = (data) => {
+  return service.post('/api/simulation/env-status', data)
+}
+
diff --git a/frontend/src/views/SimulationRunView.vue b/frontend/src/views/SimulationRunView.vue
index c12da8a..5302e8e 100644
--- a/frontend/src/views/SimulationRunView.vue
+++ b/frontend/src/views/SimulationRunView.vue
@@ -71,7 +71,7 @@ import { useRoute, useRouter } from 'vue-router'
 import GraphPanel from '../components/GraphPanel.vue'
 import Step3Simulation from '../components/Step3Simulation.vue'
 import { getProject, getGraphData } from '../api/graph'
-import { getSimulation } from '../api/simulation'
+import { getSimulation, stopSimulation, closeSimulationEnv, getEnvStatus } from '../api/simulation'
 
 const route = useRoute()
 const router = useRouter()
@@ -142,7 +142,50 @@ const toggleMaximize = (target) => {
   }
 }
 
-const handleGoBack = () => {
+const handleGoBack = async () => {
+  // 在返回 Step 2 之前，先关闭正在运行的模拟
+  addLog('准备返回 Step 2，正在关闭模拟...')
+  
+  // 停止轮询
+  stopGraphRefresh()
+  
+  try {
+    // 先尝试优雅关闭模拟环境
+    const envStatusRes = await getEnvStatus({ simulation_id: currentSimulationId.value })
+    
+    if (envStatusRes.success && envStatusRes.data?.env_alive) {
+      addLog('正在关闭模拟环境...')
+      try {
+        await closeSimulationEnv({ 
+          simulation_id: currentSimulationId.value,
+          timeout: 10
+        })
+        addLog('✓ 模拟环境已关闭')
+      } catch (closeErr) {
+        addLog(`关闭模拟环境失败，尝试强制停止...`)
+        try {
+          await stopSimulation({ simulation_id: currentSimulationId.value })
+          addLog('✓ 模拟已强制停止')
+        } catch (stopErr) {
+          addLog(`强制停止失败: ${stopErr.message}`)
+        }
+      }
+    } else {
+      // 环境未运行，检查是否需要停止进程
+      if (isSimulating.value) {
+        addLog('正在停止模拟进程...')
+        try {
+          await stopSimulation({ simulation_id: currentSimulationId.value })
+          addLog('✓ 模拟已停止')
+        } catch (err) {
+          addLog(`停止模拟失败: ${err.message}`)
+        }
+      }
+    }
+  } catch (err) {
+    addLog(`检查模拟状态失败: ${err.message}`)
+  }
+  
   // 返回到 Step 2 (环境搭建)
   router.push({ name: 'Simulation', params: { simulationId: currentSimulationId.value } })
 }
diff --git a/frontend/src/views/SimulationView.vue b/frontend/src/views/SimulationView.vue
index ad41e08..1e218d6 100644
--- a/frontend/src/views/SimulationView.vue
+++ b/frontend/src/views/SimulationView.vue
@@ -69,7 +69,7 @@ import { useRoute, useRouter } from 'vue-router'
 import GraphPanel from '../components/GraphPanel.vue'
 import Step2EnvSetup from '../components/Step2EnvSetup.vue'
 import { getProject, getGraphData } from '../api/graph'
-import { getSimulation } from '../api/simulation'
+import { getSimulation, stopSimulation, getEnvStatus, closeSimulationEnv } from '../api/simulation'
 
 const route = useRoute()
 const router = useRouter()
@@ -171,6 +171,70 @@ const handleNextStep = (params = {}) => {
 }
 
 // --- Data Logic ---
+
+/**
+ * 检查并关闭正在运行的模拟
+ * 当用户从 Step 3 返回到 Step 2 时，默认用户要退出模拟
+ */
+const checkAndStopRunningSimulation = async () => {
+  if (!currentSimulationId.value) return
+  
+  try {
+    // 先检查模拟环境是否存活
+    const envStatusRes = await getEnvStatus({ simulation_id: currentSimulationId.value })
+    
+    if (envStatusRes.success && envStatusRes.data?.env_alive) {
+      addLog('检测到模拟环境正在运行，正在关闭...')
+      
+      // 尝试优雅关闭模拟环境
+      try {
+        const closeRes = await closeSimulationEnv({ 
+          simulation_id: currentSimulationId.value,
+          timeout: 10  // 10秒超时
+        })
+        
+        if (closeRes.success) {
+          addLog('✓ 模拟环境已关闭')
+        } else {
+          addLog(`关闭模拟环境失败: ${closeRes.error || '未知错误'}`)
+          // 如果优雅关闭失败，尝试强制停止
+          await forceStopSimulation()
+        }
+      } catch (closeErr) {
+        addLog(`关闭模拟环境异常: ${closeErr.message}`)
+        // 如果优雅关闭异常，尝试强制停止
+        await forceStopSimulation()
+      }
+    } else {
+      // 环境未运行，但可能进程还在，检查模拟状态
+      const simRes = await getSimulation(currentSimulationId.value)
+      if (simRes.success && simRes.data?.status === 'running') {
+        addLog('检测到模拟状态为运行中，正在停止...')
+        await forceStopSimulation()
+      }
+    }
+  } catch (err) {
+    // 检查环境状态失败不影响后续流程
+    console.warn('检查模拟状态失败:', err)
+  }
+}
+
+/**
+ * 强制停止模拟
+ */
+const forceStopSimulation = async () => {
+  try {
+    const stopRes = await stopSimulation({ simulation_id: currentSimulationId.value })
+    if (stopRes.success) {
+      addLog('✓ 模拟已强制停止')
+    } else {
+      addLog(`强制停止模拟失败: ${stopRes.error || '未知错误'}`)
+    }
+  } catch (err) {
+    addLog(`强制停止模拟异常: ${err.message}`)
+  }
+}
+
 const loadSimulationData = async () => {
   try {
     addLog(`加载模拟数据: ${currentSimulationId.value}`)
@@ -222,8 +286,13 @@ const refreshGraph = () => {
   }
 }
 
-onMounted(() => {
+onMounted(async () => {
   addLog('SimulationView 初始化')
+  
+  // 检查并关闭正在运行的模拟（用户从 Step 3 返回时）
+  await checkAndStopRunningSimulation()
+  
+  // 加载模拟数据
   loadSimulationData()
 })
 </script>