Yikes! These scare me:
set-variable = table_cache=15000 -- 200 would be better
set-variable = max_connections=5000 -- I have never seen a machine needing more than 1000; 100 might be more reasonable.
These may be in trouble
thread_stack = 128k -- I thought it needed to be at least 192K
set-variable = key_buffer=312M -- How much RAM do you have?
Are you using MyISAM or InnoDB?
More tuning tips:
http://mysql.rjweb.org/doc.php/memory
> The CPU usage of my mysql is between 300 ~ 700% range every time.
Almost always that is due to inefficient indexes or queries. Let's see the queries that are taking longest. Also, provide SHOW CREATE TABLE.
> All optimizations have been made in consultations
Sorry, but I am skeptical.