@Eng.Mohamed 

When the CPU is high, check the system logs to see if there may be a clue there of what is being done at that time.

@Tony 

Hi Tony,

Thanks for your reply, Actually I checked the logs and I found most repetitive log during all the time is as below snapshot. Please help if you know how search about below log codes.

@Eng.Mohamed 

Those logs appeard for other routers as well. The latest one was with the Archer A7, which firmware resolved. I would recommend getting a hold of our support so they may look into it further for you.

@Tony 

Hi Tony,

Its same router also please how can i get help from support team noticing that i have the log file of my router.

Thanks for your help

@Eng.Mohamed 

Here are the ways you can reach them:

Live Chat: link
Phone: link
E-mail: link

@Tony 

Thanks a lot Tony,

Will try to contact them hopping they can help me. 

I am currently using an Archer 6 (1.1.7 Build 20201010 rel.49458(5553)) as my "main" router connected to my internet cable modem.  Because of the topography and the solid walls of my house I have 3 other routers set up  as access points throughout the house and connected to the Archer via cat6 cables.

In any event, the Archer kept running at 100% CPU load constantly and crashing (rebooting itself?) with some regularity.  I was going to change it completely but then remembered I had bought a very basic $20 network switch at some point (this one in fact https://smile.amazon.com/gp/product/B00A121WN6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1),  and decided to try connecting my secondary APs to the switch instead of directly to Archer (so that the only thing hard wired into Archer other than the cable modem was the switch).  The effect was immediate and much more profound than I expected - the Archer CPU load is now routinely under 10% (often 5-6%, and jumps up in spurts periodically as I guess it does its thing). Best part is, I have not had internet connectivity issues/drops since I did this about a month ago, and did not need to buy a more robust (and expensive) router for the time being. I hope this helps!