After several tests, there is finally a way to restore the frame number and picture stability to the level of previous versions, and it will not start to drop frames after playing a few games.
solution
1. Notepad Open the folder x:\ My Documents \ Call of Duty Modern Warfare \ adv_options.ini file in the player.
2. Modify the number RendererWorkerCount = the number of threads in your cpu (not the number of cores but the number of threads), save and exit.
3. Change the attribute of this ini file to "Read Only", otherwise Battle.net will automatically change the value back to the default value when entering the game.
As long as you know your cpu model, online search can naturally see several cores and threads.