Hi lenghui.
If the default System Manager ID and PIN are not working, we will be glad to assist you with resetting the printer.
Please contact our Enterprise & Desktop Solutions Divisions Group at 1-800-OK-CANON (652-2666), Monday - Friday 10:00 a.m. to 6:30 p.m. ET (excluding holidays).
I apologize for any inconvenience this may cause; however, these steps need to be provided by phone with a technician assisting you through it.