所有跟mysql相关进程都停止掉， 然后终端输入：
cd ~/
sudo rm /usr/local/mysql
sudo rm -rf /usr/local/var/mysql
sudo rm -rf /usr/local/mysql*
sudo rm -rf /Library/StartupItems/MySQLCOM
sudo rm -rf /Library/PreferencePanes/My*
vim /etc/hostconfig and removed the line MYSQLCOM=-YES-rm -rf ~/Library/PreferencePanes/My*
sudo rm -rf /Library/Receipts/mysql*
sudo rm -rf /Library/Receipts/MySQL*
sudo rm -rf /var/db/receipts/com.mysql.*
然后重新安装就行了