mysql默认安装的root用户是没有远程登录权限的：

mysql -u root -p

mysql> use mysql;
mysql> SELECT host, user FROM user WHERE user = 'root';
+-----------+------+
| host      | user |
+-----------+------+
| localhost | root |
+-----------+------+

只能够从机器上登录

使用：
<password>部分替换为需要使用的密码

 CREATE USER 'root'@'%' IDENTIFIED BY '<password>'; GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' WITH GRANT OPTION;

即可

mysql> use mysql;
mysql> SELECT host, user FROM user WHERE user = 'root';
+-----------+------+
| host      | user |
+-----------+------+
| %         | root |
| localhost | root |
+-----------+------+

测试：