Methane accumulation and gas overrun accident bring heavy hidden danger to the production safety in coalmines, irregularly maintenance and switch of fan and switch fault face great challenge from safety standard such as methane accumulation and gas overrunning. This paper proposed standby fan originally, guaranteed continuity of power supply during main fan switching, It demonstrate the scientific of the scheme based on fluid mechanics, meanwhile, analyze automatic control, power requirements and coal conditions. At last, it is concluded that the scheme offer the universal implemental foundation and has huge significance to the mine safety production.