diff --git a/web/frontend/src/App.vue b/web/frontend/src/App.vue
index 852ab45..491e341 100644
--- a/web/frontend/src/App.vue
+++ b/web/frontend/src/App.vue
@@ -2,8 +2,10 @@
 import { computed } from 'vue'
 import { useRouter, useRoute } from 'vue-router'
 import { useAuthStore } from '@/stores/auth'
+import { useThemeStore } from '@/stores/theme'
 
 const auth = useAuthStore()
+const theme = useThemeStore()
 const router = useRouter()
 const route = useRoute()
 
@@ -39,7 +41,16 @@ function logout() {
             {{ auth.isAdmin ? '管理员' : '普通用户' }}
           </el-tag>
         </div>
-        <el-button type="primary" link @click="logout">退出登录</el-button>
+        <div class="right">
+          <el-switch
+            v-model="theme.isDark"
+            inline-prompt
+            active-text="暗"
+            inactive-text="亮"
+            style="--el-switch-on-color: #2c3e50"
+          />
+          <el-button type="primary" link @click="logout">退出登录</el-button>
+        </div>
       </el-header>
       <el-main>
         <router-view />
@@ -57,6 +68,10 @@ body,
   margin: 0;
   font-family: -apple-system, BlinkMacSystemFont, 'PingFang SC', 'Microsoft YaHei', sans-serif;
 }
+body {
+  background-color: var(--el-bg-color-page);
+  color: var(--el-text-color-primary);
+}
 .app {
   height: 100%;
 }
@@ -77,14 +92,19 @@ body,
   display: flex;
   justify-content: space-between;
   align-items: center;
-  background: #fff;
-  border-bottom: 1px solid #ebeef5;
+  background: var(--el-bg-color);
+  border-bottom: 1px solid var(--el-border-color-light);
 }
 .user {
   display: flex;
   align-items: center;
   gap: 10px;
 }
+.right {
+  display: flex;
+  align-items: center;
+  gap: 16px;
+}
 .el-menu {
   border-right: none !important;
 }
diff --git a/web/frontend/src/components/KLineChart.vue b/web/frontend/src/components/KLineChart.vue
index 2613fec..72cfe9a 100644
--- a/web/frontend/src/components/KLineChart.vue
+++ b/web/frontend/src/components/KLineChart.vue
@@ -2,12 +2,23 @@
 import { onBeforeUnmount, onMounted, ref, watch } from 'vue'
 import * as echarts from 'echarts'
 import type { Candle } from '@/api/candles'
+import { useThemeStore } from '@/stores/theme'
 
 const props = defineProps<{ data: Candle[] }>()
+const theme = useThemeStore()
 
 const containerRef = ref<HTMLDivElement | null>(null)
 let chart: echarts.ECharts | null = null
 
+function ensureChart() {
+  if (!containerRef.value) return
+  if (chart) {
+    chart.dispose()
+    chart = null
+  }
+  chart = echarts.init(containerRef.value, theme.isDark ? 'dark' : undefined)
+}
+
 function render() {
   if (!chart) return
   const dates = props.data.map((c) => c.trade_date)
@@ -17,6 +28,7 @@ function render() {
 
   chart.setOption(
     {
+      backgroundColor: 'transparent',
       tooltip: { trigger: 'axis', axisPointer: { type: 'cross' } },
       legend: { data: ['K 线', '持仓量'], top: 0 },
       grid: [
@@ -69,11 +81,9 @@ function resize() {
 }
 
 onMounted(() => {
-  if (containerRef.value) {
-    chart = echarts.init(containerRef.value)
-    render()
-    window.addEventListener('resize', resize)
-  }
+  ensureChart()
+  render()
+  window.addEventListener('resize', resize)
 })
 
 onBeforeUnmount(() => {
@@ -83,6 +93,13 @@ onBeforeUnmount(() => {
 })
 
 watch(() => props.data, render, { deep: true })
+watch(
+  () => theme.isDark,
+  () => {
+    ensureChart()
+    render()
+  },
+)
 </script>
 
 <template>
diff --git a/web/frontend/src/main.ts b/web/frontend/src/main.ts
index 4f57c49..8d5b520 100644
--- a/web/frontend/src/main.ts
+++ b/web/frontend/src/main.ts
@@ -3,6 +3,7 @@ import { createPinia } from 'pinia'
 import ElementPlus from 'element-plus'
 import zhCn from 'element-plus/es/locale/lang/zh-cn'
 import 'element-plus/dist/index.css'
+import 'element-plus/theme-chalk/dark/css-vars.css'
 
 import App from './App.vue'
 import router from './router'
diff --git a/web/frontend/src/stores/theme.ts b/web/frontend/src/stores/theme.ts
new file mode 100644
index 0000000..9adfd72
--- /dev/null
+++ b/web/frontend/src/stores/theme.ts
@@ -0,0 +1,32 @@
+import { defineStore } from 'pinia'
+import { ref, watch } from 'vue'
+
+const STORAGE_KEY = 'trade.theme'
+type Mode = 'dark' | 'light'
+
+function detectInitial(): boolean {
+  const saved = localStorage.getItem(STORAGE_KEY) as Mode | null
+  if (saved === 'dark') return true
+  if (saved === 'light') return false
+  return window.matchMedia?.('(prefers-color-scheme: dark)').matches ?? false
+}
+
+function apply(isDark: boolean) {
+  document.documentElement.classList.toggle('dark', isDark)
+}
+
+export const useThemeStore = defineStore('theme', () => {
+  const isDark = ref(detectInitial())
+  apply(isDark.value)
+
+  watch(isDark, (v) => {
+    apply(v)
+    localStorage.setItem(STORAGE_KEY, v ? 'dark' : 'light')
+  })
+
+  function toggle() {
+    isDark.value = !isDark.value
+  }
+
+  return { isDark, toggle }
+})
diff --git a/web/frontend/src/views/AdminUsersView.vue b/web/frontend/src/views/AdminUsersView.vue
index ad58df4..57ad2cb 100644
--- a/web/frontend/src/views/AdminUsersView.vue
+++ b/web/frontend/src/views/AdminUsersView.vue
@@ -193,6 +193,6 @@ onMounted(reload)
   display: flex;
   justify-content: space-between;
   align-items: center;
-  color: #606266;
+  color: var(--el-text-color-regular);
 }
 </style>
diff --git a/web/frontend/src/views/LoginView.vue b/web/frontend/src/views/LoginView.vue
index 5a0a6d2..7645cbc 100644
--- a/web/frontend/src/views/LoginView.vue
+++ b/web/frontend/src/views/LoginView.vue
@@ -69,7 +69,8 @@ async function submit() {
 .card {
   width: 360px;
   padding: 36px 32px;
-  background: #fff;
+  background: var(--el-bg-color);
+  color: var(--el-text-color-primary);
   border-radius: 8px;
   box-shadow: 0 12px 32px rgba(0, 0, 0, 0.18);
 }
@@ -79,7 +80,7 @@ async function submit() {
 }
 .hint {
   margin: 0 0 24px;
-  color: #909399;
+  color: var(--el-text-color-secondary);
   font-size: 12px;
   text-align: center;
 }
diff --git a/web/frontend/src/views/ScoresView.vue b/web/frontend/src/views/ScoresView.vue
index 8333451..b32bdc3 100644
--- a/web/frontend/src/views/ScoresView.vue
+++ b/web/frontend/src/views/ScoresView.vue
@@ -120,6 +120,6 @@ onMounted(async () => {
   padding: 12px 16px;
 }
 .score-table {
-  background: #fff;
+  background: var(--el-bg-color);
 }
 </style>