diff --git a/.env.example b/.env.example
index 3ead6cd..6449e65 100644
--- a/.env.example
+++ b/.env.example
@@ -1,4 +1,5 @@
 DEEPSEEK_API_KEY=your-api-key
+SERVICE_PORT=8000
 DEEPSEEK_BASE_URL=https://api.deepseek.com
 DEEPSEEK_MODEL=deepseek-v4-flash
 DEFAULT_SYSTEM_PROMPT=You are a helpful assistant.
diff --git a/README.md b/README.md
index 8619459..875130e 100644
--- a/README.md
+++ b/README.md
@@ -6,13 +6,14 @@
 
 ```bash
 uv sync
-export DEEPSEEK_API_KEY="your-api-key"
+cp .env.example .env
+# 编辑 .env 并填写 DEEPSEEK_API_KEY
 uv run uvicorn main:app --reload
 ```
 
 服务默认运行在 `http://127.0.0.1:8000`，交互式 API 文档位于 `/docs`。
 
-可通过环境变量配置 `DEEPSEEK_BASE_URL`、`DEEPSEEK_MODEL`、`DEFAULT_SYSTEM_PROMPT` 和 `CHAT_DATA_DIR`，完整示例见 `.env.example`。第一版应只使用一个 Uvicorn worker。
+服务会自动加载项目根目录的 `.env`，已有系统环境变量优先级更高。可配置 `DEEPSEEK_BASE_URL`、`DEEPSEEK_MODEL`、`DEFAULT_SYSTEM_PROMPT` 和 `CHAT_DATA_DIR`，完整示例见 `.env.example`。第一版应只使用一个 Uvicorn worker。
 
 ## 使用
 
diff --git a/config.py b/config.py
index a6cd6de..83018d9 100644
--- a/config.py
+++ b/config.py
@@ -2,9 +2,12 @@ from dataclasses import dataclass
 from pathlib import Path
 import os
 
+from dotenv import load_dotenv
+
 
 @dataclass(frozen=True, slots=True)
 class Settings:
+    port: int
     api_key: str | None
     base_url: str
     model: str
@@ -13,7 +16,9 @@ class Settings:
 
     @classmethod
     def from_env(cls) -> "Settings":
+        load_dotenv(dotenv_path=Path.cwd() / ".env", override=False)
         return cls(
+            port=int(os.getenv("SERVICE_PORT", "8000")),
             api_key=os.getenv("DEEPSEEK_API_KEY"),
             base_url=os.getenv("DEEPSEEK_BASE_URL", "https://api.deepseek.com"),
             model=os.getenv("DEEPSEEK_MODEL", "deepseek-v4-flash"),
diff --git a/main.py b/main.py
index 8bf6f50..b76f231 100644
--- a/main.py
+++ b/main.py
@@ -1,7 +1,8 @@
 from app import app
-
+from config import Settings
 
 if __name__ == "__main__":
     import uvicorn
 
-    uvicorn.run("main:app", host="0.0.0.0", port=8000, reload=True)
+    settings = Settings.from_env()
+    uvicorn.run("main:app", host="0.0.0.0", port=settings.port, reload=True)
diff --git a/pyproject.toml b/pyproject.toml
index 6156b03..ebb81e1 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -8,6 +8,7 @@ dependencies = [
     "fastapi>=0.115.0",
     "httpx[socks]>=0.28.0",
     "openai>=1.55.0",
+    "python-dotenv>=1.0.0",
     "uvicorn[standard]>=0.32.0",
 ]
 
diff --git a/tests/test_api.py b/tests/test_api.py
index ac057b9..81c3f17 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -49,6 +49,7 @@ class FakeClient:
 def client_and_provider(tmp_path: Path) -> tuple[TestClient, FakeClient]:
     provider = FakeClient()
     settings = Settings(
+        port=8000,
         api_key=None,
         base_url="https://api.deepseek.com",
         model="deepseek-v4-flash",
@@ -66,6 +67,18 @@ def create_session(client: TestClient, **body: str) -> str:
     return response.json()["session_id"]
 
 
+def test_settings_load_api_key_from_dotenv(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    monkeypatch.chdir(tmp_path)
+    monkeypatch.delenv("DEEPSEEK_API_KEY", raising=False)
+    (tmp_path / ".env").write_text("DEEPSEEK_API_KEY=test-key\n")
+
+    settings = Settings.from_env()
+
+    assert settings.api_key == "test-key"
+
+
 def test_create_session_uses_default_prompt(
     client_and_provider: tuple[TestClient, FakeClient], tmp_path: Path
 ) -> None:
diff --git a/uv.lock b/uv.lock
index 6ea1721..a31efdb 100644
--- a/uv.lock
+++ b/uv.lock
@@ -366,6 +366,7 @@ dependencies = [
     { name = "fastapi" },
     { name = "httpx", extra = ["socks"] },
     { name = "openai" },
+    { name = "python-dotenv" },
     { name = "uvicorn", extra = ["standard"] },
 ]
 
@@ -379,6 +380,7 @@ requires-dist = [
     { name = "fastapi", specifier = ">=0.115.0" },
     { name = "httpx", extras = ["socks"], specifier = ">=0.28.0" },
     { name = "openai", specifier = ">=1.55.0" },
+    { name = "python-dotenv", specifier = ">=1.0.0" },
     { name = "uvicorn", extras = ["standard"], specifier = ">=0.32.0" },
 ]