Mysql Master Slave replication performance is too low

I have implemented Master Slave Replication.

The slave can't keep up with progress.

How can I find out the problem and optimize the config?

OS: CentOS 6.8
Mysql 5.6.35
Master => Slave 3-5 Mbps

           Slave_IO_State: Waiting for master to send event
              Master_Host: **.**.**.**
              Master_User: ********
              Master_Port: 3306
            Connect_Retry: 60
          Master_Log_File: binlog.000095
      Read_Master_Log_Pos: 297639485
           Relay_Log_File: mysqld-relay-bin.000050
            Relay_Log_Pos: 644337677
    Relay_Master_Log_File: binlog.000083
         Slave_IO_Running: Yes
        Slave_SQL_Running: Yes
          Replicate_Do_DB:
      Replicate_Ignore_DB:
       Replicate_Do_Table:
   Replicate_Ignore_Table:
  Replicate_Wild_Do_Table:   Replicate_Wild_Ignore_Table:
               Last_Errno: 0
               Last_Error:
             Skip_Counter: 0
      Exec_Master_Log_Pos: 644337473
          Relay_Log_Space: 13252726053
          Until_Condition: None
           Until_Log_File:
            Until_Log_Pos: 0
       Master_SSL_Allowed: No
       Master_SSL_CA_File:
       Master_SSL_CA_Path:
          Master_SSL_Cert:
        Master_SSL_Cipher:
           Master_SSL_Key:
    Seconds_Behind_Master: 119951 Master_SSL_Verify_Server_Cert: No
            Last_IO_Errno: 0
            Last_IO_Error:
           Last_SQL_Errno: 0
           Last_SQL_Error:   Replicate_Ignore_Server_Ids:
         Master_Server_Id: 1
              Master_UUID: bada755f-d361-11e6-b53e-d4ae52b21cd5
         Master_Info_File: mysql.slave_master_info
                SQL_Delay: 0
      SQL_Remaining_Delay: NULL
  Slave_SQL_Running_State: System lock
       Master_Retry_Count: 86400
              Master_Bind:
  Last_IO_Error_Timestamp:
 Last_SQL_Error_Timestamp:
           Master_SSL_Crl:
       Master_SSL_Crlpath:
       Retrieved_Gtid_Set: bada755f-d361-11e6-b53e-d4ae52b21cd5:281172-14941959
        Executed_Gtid_Set: bada755f-d361-11e6-b53e-d4ae52b21cd5:1-11696260
            Auto_Position: 1