To reduce the heating energy consumption of electric vehicles in winter, a switching control strategy for multiple heating modes formed by three heat sources, including air, motor waste heat, and positive temperature coefficient (PTC) heaters, is designed. Firstly, an integrated thermal management system (ITMS) simulation model for the heat pump air conditioning system, battery thermal management system, and motor thermal management system is established based on the AMESim software. Secondly, the influence of ambient temperature and motor outlet coolant temperature on the heating performance of three cabin heating modes is studied. Specifically, the three cabin heating modes include the pure motor waste heat source heat pump mode, the pure air-source heat pump mode, and the dual heat source heat pump mode with waste heat source and air source. Based on the analysis results, the opening and closing strategies for the three cabin heating modes are discussed. The optimum mode of using motor waste heat and PTC heater to heat the battery is further discussed. Based on the heating priority of the cabin and battery, as well as the maximum heating capacity of the heating modes including the air source, a switching control strategy for multiple heating modes is studied. The results show that compared to the traditional heating method of using the air-source heat pump for cabin heating and PTC heater for battery heating, the proposed control strategy in this paper can reduce the energy consumption of the studied electric vehicle by 18.3% if heating for 2 hours at the ambient temperature of -5 °C. This research provides an effective solution for heating the cabin and battery of electric vehicles in cold weather, significantly reducing energy consumption and extending the driving range.