diff --git a/.ci/Dockerfile b/.ci/Dockerfile
index 488c81d..727ffcd 100644
--- a/.ci/Dockerfile
+++ b/.ci/Dockerfile
@@ -1,13 +1,14 @@
-FROM ubuntu:24.04
+# 第一阶段：构建基础环境（这层很少变动，缓存命中率高）
+FROM ubuntu:24.04 AS builder-base
 
-# 1. 安装完整的交叉编译环境 (Clang + MinGW-w64)
+# 1. 设置APT镜像源加速（可选，可替换为国内源如 mirrors.aliyun.com）
+RUN sed -i 's/archive.ubuntu.com/mirrors.aliyun.com/g' /etc/apt/sources.list && \
+    sed -i 's/security.ubuntu.com/mirrors.aliyun.com/g' /etc/apt/sources.list
+
+# 2. 一次性安装所有系统依赖和工具链（这一层如果不变，会完全复用缓存）
 RUN apt-get update && \
     apt-get install -y --no-install-recommends \
-        wget gnupg ca-certificates && \
-    wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | apt-key add - && \
-    echo "deb http://apt.llvm.org/noble/ llvm-toolchain-noble-19 main" > /etc/apt/sources.list.d/llvm.list && \
-    apt-get update && \
-    apt-get install -y --no-install-recommends \
+        wget gnupg ca-certificates \
         clang-19 lld-19 libc++-19-dev libc++abi-19-dev \
         mingw-w64 g++-mingw-w64 \
         tar git curl \
@@ -16,20 +17,32 @@ RUN apt-get update && \
     update-alternatives --install /usr/bin/clang++ clang++ /usr/bin/clang++-19 100 && \
     update-alternatives --install /usr/bin/ld ld /usr/bin/ld.lld-19 100
 
-# 2. 设置非root用户
+# 3. 安装xmake（独立一层，xmake更新时才需要重建）
+RUN wget -O /usr/local/bin/xmake \
+    https://git.fig-lang.cn/PuqiAR/xmake-binary-copy/raw/commit/989d1f2dabb0bc8d5981a5f900c2cf7c2ac78ee4/xmake-bundle-v3.0.5.linux.x86_64 && \
+    chmod +x /usr/local/bin/xmake
+
+# 第二阶段：创建最终镜像（极轻量）
+FROM ubuntu:24.04
+
+# 1. 仅复制必要的运行时文件
+COPY --from=builder-base /usr/local/bin/xmake /usr/local/bin/xmake
+COPY --from=builder-base /usr/bin/clang++ /usr/bin/clang++
+COPY --from=builder-base /usr/bin/clang /usr/bin/clang
+COPY --from=builder-base /usr/bin/ld.lld /usr/bin/ld.lld
+# 复制MinGW交叉编译器的库和头文件（关键！）
+COPY --from=builder-base /usr/x86_64-w64-mingw32 /usr/x86_64-w64-mingw32
+# 复制标准C++库
+COPY --from=builder-base /usr/lib/llvm-19 /usr/lib/llvm-19
+
+# 2. 创建非root用户
 RUN useradd -m -s /bin/bash builder
 
-# 3. 切换到builder用户安装xmake
+# 3. 设置默认用户
 USER builder
 WORKDIR /home/builder
 
-RUN wget -O xmake https://git.fig-lang.cn/PuqiAR/xmake-binary-copy/raw/commit/989d1f2dabb0bc8d5981a5f900c2cf7c2ac78ee4/xmake-bundle-v3.0.5.linux.x86_64 && \
-    chmod +x xmake && \
-    ./xmake --version 2>&1 | head -1
-
-# 4. 切回root，将xmake安装到系统路径
-USER root
-RUN cp /home/builder/xmake /usr/local/bin/xmake && \
-    chmod +x /usr/local/bin/xmake
-
-USER builder
\ No newline at end of file
+# 4. 验证安装（可选）
+RUN xmake --version | head -1 && \
+    clang++ --version | head -1 && \
+    echo "构建环境就绪"
\ No newline at end of file