1、如果知道root密码：

mysql -u root -p  

输入密码 

use mysql;

UPDATE user SET Password = PASSWORD(‘newpass‘) WHERE user = ‘root‘;

FLUSH PRIVILEGES;

quit;

2、如果不知道密码

service mysqld stop;

mysqld_safe
--skip-grant-tables&
mysql -u root mysql;
UPDATE
user
SET
password
=
PASSWORD
(
"new password"
)
WHERE
user
=
‘root‘
;
FLUSH
PRIVILEGES
;   password字段没有的话: update mysql.user set authentication_string=password(‘新密码‘) where user=‘root‘;
FLUSH 
PRIVILEGES
;