The invention relates to a sun and air mixed source heat pump constant-temperature heating system which comprises a heat collector, an aluminum rack pipe temperature sensor, an air frost point temperature sensor, a controller, a room temperature sensor, a room temperature set value device, a compressor, a condenser, a throttling device and a draught fan. The sun and air mixed source heat pump constant-temperature heating system is characterized in that the heat collector is composed of an aluminum rack pipe and serves as an evaporator, a heat insulation material and a light-transmitting cover plate are not arranged, the aluminum rack pipe is exposed in the air to directly absorb solar energy and air heat energy, the controller controls the temperature of the aluminum rack pipe to be higher than the air frost point temperature by controlling starting or speed regulating or stopping of the compressor, and therefore the aluminum rack pipe cannot be frosted; when the temperature of the aluminum rack pipe is lower than the air temperature, air heat energy is transmitted to the aluminum rack pipe, and the aluminum rack pipe absorbs the air heat energy; and when sun shines on the aluminum rack pipe and the temperature of the aluminum rack pipe is lower than the air temperature, the solar energy and the air heat energy are transmitted to the aluminum rack pipe at the same time, and the aluminum rack pipe can absorb the solar energy and the air heat energy at the same time. The sun and air mixed source heat pump constant-temperature heating system has the beneficial effects that the solar energy and the air heat energy can be absorbed at the same time, the cost is low, the efficiency is high, the heat collector is not frosted, and the sun and air mixed source heat pump constant-temperature heating system is very suitable for being used in northern high and cold areas.