Traditional fuel vehicles use the waste heat of the engine to heat the coolant, and send the heat of the coolant to the cabin through heaters and other components to increase the temperature inside the cabin. Since the electric motor has no engine, it cannot use the air conditioning solution of the traditional fuel car. Therefore, it is necessary to adopt other heating measures to adjust the air temperature, humidity and flow rate in the car in winter. At present, electric vehicles mainly adopt electric heating auxiliary air conditioning system, that is, single cooling air conditioner (AC), and external thermistor (PTC) heater auxiliary heating. There are two main schemes, one is to use PTC air heater, the other is using PTC water heating heater.