The invention discloses a pressure reducing valve control circuit and a control method thereof. The control circuit comprises an operating switch, a rectifier bridge, a valve change-over switch and a charge coil, wherein the charge coil is connected with a storage battery through the rectifier bridge; the operating switch is separately connected with a relay of a starting motor, an electromagnetic valve of a carburetor, the valve change-over switch and a flameout end of a high-voltage set; the relay of the starting motor and the electromagnetic valve of the carburetor are connected with an anode of the storage battery; and the valve change-over switch is in linkage connection with a microswitch of a pressure reducing valve. According to the control method of the pressure reducing valve control circuit, corresponding fuels are selected through the valve change-over switch, when the valve change-over switch rotates to a corresponding position, the corresponding microswitch is triggered, switch-on and switch-off of the electromagnetic valve connected with the microswitch are controlled, then switch-on and switch-off of an oil line of the carburetor can be controlled, and the circumstance that fuel oil in the carburetor combusts to cause unstable running of an engine is avoided; and by switching of different states of the operating switch, three states including starting, flameout and working of a generator are realized.