The invention discloses a plug-in hybrid power car heater system and a control method thereof. The system comprises an engine, an electric water pump, a heater water tank, a high pressure PTC, an electromagnetic valve, a high pressure accumulator, an air conditioner controller, a blower, an engine controller and a vehicle controller. According to the control method for the plug-in hybrid power car heater system, in a pure electric mode, engine cooling liquid is driven by the electric water pump to circulate, waste heat of the engine cooling liquid is fully utilized for heating, electricity consumption of the high pressure PTC is reduced, and fuel economy is improved; and the engine cooling liquid temperature interval when the engine and the electric water pump work is reasonably selected and controlled, the influence on the working time of the engine is reduced as much as possible, and different heating requirements can be met.