cd /usr/local
git remote set-url origin git://mirrors.tuna.tsinghua.edu.cn/homebrew.git
brew update
如果速度还是很慢，可以尝试以下操作： 然后重试update。
cd ~/tmp
git clone git://mirrors.tuna.tsinghua.edu.cn/homebrew.git
rm -rf /usr/local/.git
rm -rf /usr/local/Library
cp -R homebrew/.git /usr/local/
cp -R homebrew/Library /usr/local/
使用homebrew-science或者homebrew-python
cd /usr/local/Library/Taps/homebrew/homebrew-science
git remote set-url origin git://mirrors.tuna.tsinghua.edu.cn/homebrew-science.git cd /usr/local/Library/Taps/homebrew/homebrew-python
git remote set-url origin git://mirrors.tuna.tsinghua.edu.cn/homebrew-python.git brew update
来源：http://mirrors.tuna.tsinghua.edu.cn/help/#homebrew