1、在my.init文件中的[mysqld]下面加上skip-grant-tables，故名思议，就是跳过授权验证表，直接操作数据库
2、重新启动mysql (net start/stop mysql)
3、在MySQL Command Line Client用root以空密码登陆。 或者在命令行中敲命令"mysql"（path设置）
4、修改密码
mysql> use mysql;
Database changed
mysql> UPDATE user SET Password = password ('root') WHERE User = 'root';
Query OK, 2 rows affected (0.00 sec)
Rows matched: 2 Changed: 2 Warnings: 0
5、查看是否修改成功
mysql> select password from user where user='root';
+-------------------------------------------+
| password |
+-------------------------------------------+
| *81F5E21E35407D884A6CD4A731AEBFB6AF209E1B |
| *81F5E21E35407D884A6CD4A731AEBFB6AF209E1B |
+-------------------------------------------+
2 rows in set (0.00 sec)
6、刷新权限，mysql新设置用户或更改密码后需用flush privileges刷新MySQL的系统权限相关表，否则会出现拒绝访问，还有一种方法，就是重新启动mysql服务器，来使新设置生效。并退出
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
mysql> exit
Bye
7、在my.int中，把skip-grant-tables删掉，重启mysql
8、再次登陆数据库，成功
C:\Windows\system32>mysql -uroot -p
Enter password: ****
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 10
Server version: 5.1.57-community MySQL Community Server (GPL)