mysql安装位置:C:\Program Files\MySQL\MySQL Server 5.1\
一/打开cmd终端
输入:>net stop mysql
>cd C:\Program Files\MySQL\MySQL Server 5.1\bin
>mysqld --skip-grant-tables
二/打开另一个终端
>cd C:\Program Files\MySQL\MySQL Server 5.1\bin
mysql>mysql -u root
mysql> use mysql
database changed
mysql> update user set password=password("123456") where host="localhost" and user="root"; ##新密码改为123456
mysql> flush privileges;
mysql> quit
三/重启系统,完成