The invention discloses a waste heat heating system which comprises a heat exchanger (7), an after-burning boiler (8), an air processor (9), a cold water tank (10) and a hot water tank (10). The after-burning boiler (8) comprises a combustor, a flue gas passageway, an air conditioner heating medium pipeline and a water pipe. Flue gas of the combustor is communicated to the flue gas passageway. Flue gas in the flue gas passageway is used for heating the air conditioner heating medium pipeline. A heating medium in the air conditioner heating medium pipeline is used for heating the water pipe. A water circulation system is formed between the water pipe and the hot water box (11). The cold water tank (10) is used for supplementing water for the hot water tank (11). The air processor (9) comprises a draught fan and a surface air cooler. The draught fan is used for outputting air flowing through the surface air cooler. An air conditioner circulation loop is formed among the heat exchanger (7), the air conditioner heating medium pipeline and the surface air cooler. The waste heat heating system can be used for generating hot air and hot water, the problem that the process of generating hot air and hot water through waste heat is overcome, and the structure is compact.