The invention discloses an electric auxiliary heating device of an air conditioner, which comprises a heating appliance arranged inside an air-out frame and a self-resetting thermal trip and a non-self-resetting thermal trip, and is characterized in that the non-self-resetting thermal trip is located in the upper end of the heating appliance. The self-resetting thermal trip is located in the upper end, the lateral part or the middle part of the heating appliance. The heating appliance is an electric heating tube or a PTC semiconductor. When in normal use of the air conditioner, the non-self-resetting thermal trip feels the heat radiated by a heat pump and the top of the heating appliance of the electric auxiliary heating device, the temperature is low, the non-self-resetting thermal trip sets a low stated action temperature, thereby the response time of stopping work of the electric auxiliary heating device is shortened, and the deformation of the structure members is reduced. The electric auxiliary heating device of an air conditioner has dedicated design, good performance, security and practicability. The response speed of the non-self-resetting thermal trip is accelerated by changing the position thereof, and the misfire phenomenon caused by the independent starting of the electric auxiliary heating device is fundamentally avoided.