这个问题是由于我的MySQL的的的更新至8版本以上了，在安装的时候我并没有指定用户登入密码加密方式，所以默认被设置为caching_sha2_password 解决方法： 
mysql> show variables like 'default_authentication_plugin'; 
 +-------------------------------+-----------------------+ 
 | Variable_name                 | Value                | 
 +-------------------------------+-----------------------+  
 | default_authentication_plugin |caching_sha2_password |
 +-------------------------------+-----------------------+  
1 row in set (0.03 sec)  
// 查看本地mysql用户的信息  
mysql> select host,user,plugin from mysql.user; 
 +-----------+------------------+----------------------+ 
 | host      | user             | plugin               | 
 +-----------+------------------+-----------------------+
 | localhost | mysql.infoschema | caching_sha2_password| 
 | localhost | mysql.session    | caching_sha2_password|  
 | localhost | mysql.sys        | caching_sha2_password|
 | localhost | root             | caching_sha2_password| 
 +-----------+------------------+-----------------------+ 
4 rows in set (0.00 sec)  
// 注意 caching_sha2_password， 只修改root的密码加密方式就可以了 
mysql> ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY '123456';  
Query OK, 0 rows affected (0.04 sec) 
mysql> select host,user,plugin from mysql.user; 
+-----------+------------------+-----------------------+  
| host      | user             | plugin                | 
+-----------+------------------+-----------------------+  
| localhost | mysql.infoschema | caching_sha2_password | 
| localhost | mysql.session    | caching_sha2_password | 
| localhost | mysql.sys        | caching_sha2_password | 
| localhost | root             | mysql_native_password | 
 +-----------+------------------+-----------------------+ 
 4 rows in set (0.00 sec)