diff --git a/website/docs/en/guide/basic/cli.mdx b/website/docs/en/guide/basic/cli.mdx
index e279cf7e6..2897083d0 100644
--- a/website/docs/en/guide/basic/cli.mdx
+++ b/website/docs/en/guide/basic/cli.mdx
@@ -51,14 +51,33 @@ Options:
 
 ### Environment variables
 
-Rslib supports injecting env variables or expressions into the code during build, which is helpful for distinguishing the running environment or replacing constants.
-
-You can see more details in [Rsbuild - Environment variables](https://rsbuild.rs/guide/advanced/env-vars).
+Rslib supports injecting environment variables or expressions into the code during the build, which is helpful for distinguishing running environments or replacing constants. You can see more details in [Rsbuild - Environment variables](https://rsbuild.rs/guide/advanced/env-vars).
+
+By default, Rslib sets the `process.env.NODE_ENV` environment variable, which is always `'production'` during the build. If you need to distinguish watch mode to dynamically set different configurations, you can set as follows:
+
+```ts title="rslib.config.ts"
+import { defineConfig } from '@rslib/core';
+
+const isWatch = process.argv.includes('--watch');
+
+export default defineConfig({
+  lib: [
+    {
+      format: 'esm',
+    },
+  ],
+  source: {
+    alias: {
+      '@request': isWatch ? './src/request.dev.js' : './src/request.prod.js',
+    },
+  },
+});
+```
 
 ::: note
 
-- If [format](/config/lib/format) is `esm` or `cjs`, `process.env.NODE_ENV` will be preserved in the build output.
-- If [format](/config/lib/format) is `mf` or `umd`, `process.env.NODE_ENV` will be replaced to ensure that the output can run in the browser.
+- If [format](/config/lib/format) is `esm` or `cjs`, `process.env.NODE_ENV` in source code will be preserved in the build output.
+- If [format](/config/lib/format) is `mf` or `umd`, `process.env.NODE_ENV` in source code will be replaced to ensure that the output can run in the browser.
 
 :::
 
diff --git a/website/docs/en/guide/basic/configure-rslib.mdx b/website/docs/en/guide/basic/configure-rslib.mdx
index dfdc261c5..c8ab744d7 100644
--- a/website/docs/en/guide/basic/configure-rslib.mdx
+++ b/website/docs/en/guide/basic/configure-rslib.mdx
@@ -168,7 +168,7 @@ When using Node.js's native loader, please note the following limitations:
 
 ## Using environment variables
 
-In the configuration file, you can use Node.js environment variables such as `process.env.NODE_ENV` to dynamically set different configurations:
+In the configuration file, you can use Node.js environment variables to dynamically set different configurations:
 
 ```ts title="rslib.config.ts"
 import { defineConfig } from '@rslib/core';
@@ -181,10 +181,10 @@ export default defineConfig({
   ],
   source: {
     alias: {
-      '@request':
-        process.env.NODE_ENV === 'development'
-          ? './src/request.dev.js'
-          : './src/request.prod.js',
+      '@language':
+        process.env.LANGUAGE === 'en'
+          ? './src/language/en.js'
+          : './src/language/zh.js',
     },
   },
 });
diff --git a/website/docs/zh/guide/basic/cli.mdx b/website/docs/zh/guide/basic/cli.mdx
index 27c1df60b..6d592d71c 100644
--- a/website/docs/zh/guide/basic/cli.mdx
+++ b/website/docs/zh/guide/basic/cli.mdx
@@ -51,14 +51,33 @@ Options:
 
 ### 环境变量
 
-Rslib 支持在构建过程中向代码中注入环境变量或表达式，这对于区分运行环境、替换常量值等场景很有帮助。
-
-你可以查看 [Rsbuild - 环境变量](https://rsbuild.rs/zh/guide/advanced/env-vars) 了解更多详细信息。
+Rslib 支持在构建过程中向代码中注入环境变量或表达式，这对于区分运行环境、替换常量值等场景很有帮助。你可以查看 [Rsbuild - 环境变量](https://rsbuild.rs/zh/guide/advanced/env-vars) 了解更多详细信息。
+
+默认情况下，Rslib 会自动设置 `process.env.NODE_ENV` 环境变量，在 build 时始终为 `'production'`。如果你需要区分 watch 模式来动态写入不同的配置，可以如下：
+
+```ts title="rslib.config.ts"
+import { defineConfig } from '@rslib/core';
+
+const isWatch = process.argv.includes('--watch');
+
+export default defineConfig({
+  lib: [
+    {
+      format: 'esm',
+    },
+  ],
+  source: {
+    alias: {
+      '@request': isWatch ? './src/request.dev.js' : './src/request.prod.js',
+    },
+  },
+});
+```
 
 ::: note
 
-- 当 [format](/config/lib/format) 设置为 `esm` 或 `cjs` 时，`process.env.NODE_ENV` 会在构建产物中被保留。
-- 当 [format](/config/lib/format) 设置为 `mf` 或 `umd` 时，`process.env.NODE_ENV` 将被替换，以确保构建产物可以在浏览器中运行。
+- 当 [format](/config/lib/format) 设置为 `esm` 或 `cjs` 时，源代码中的 `process.env.NODE_ENV` 会在构建产物中被保留。
+- 当 [format](/config/lib/format) 设置为 `mf` 或 `umd` 时，源代码中的 `process.env.NODE_ENV` 将被替换，以确保构建产物可以在浏览器中运行。
 
 :::
 
diff --git a/website/docs/zh/guide/basic/configure-rslib.mdx b/website/docs/zh/guide/basic/configure-rslib.mdx
index 8b14fb5ca..c177e1d8b 100644
--- a/website/docs/zh/guide/basic/configure-rslib.mdx
+++ b/website/docs/zh/guide/basic/configure-rslib.mdx
@@ -168,7 +168,7 @@ Rslib 提供了三种配置文件加载方式：
 
 ## 使用环境变量
 
-在配置文件中，你可以使用 `process.env.NODE_ENV` 等 Node.js 环境变量，来动态写入不同的配置：
+在配置文件中，你可以使用 Node.js 环境变量，来动态写入不同的配置：
 
 ```ts title="rslib.config.ts"
 import { defineConfig } from '@rslib/core';
@@ -181,10 +181,10 @@ export default defineConfig({
   ],
   source: {
     alias: {
-      '@request':
-        process.env.NODE_ENV === 'development'
-          ? './src/request.dev.js'
-          : './src/request.prod.js',
+      '@language':
+        process.env.LANGUAGE === 'en'
+          ? './src/language/en.js'
+          : './src/language/zh.js',
     },
   },
 });