The invention discloses a defrosting control method. The method comprises the following steps that (1), the air temperature Ts and the coil pipe temperature Tg close to the position of an evaporator refrigerant inlet are detected according to the period t; (2), the difference value deltaT between the air temperature Ts and the coil pipe temperature Tg is calculated; and (3), if the difference value deltaT in the step (2) is not larger than a first set threshold value, the system enters a defrosting process, otherwise, the system operates a heating process. The defrosting judgment mechanism ofthe defrosting control method is based on the growth characteristics and the distribution rule of a frost layer in an evaporator frosting process, judgment is accurate, defrosting on demand can be realized, the phenomenon that false defrosting frequently occurs by an existing double-temperature sensor method in a cold and dry environment is avoided, and the energy efficiency ratio and reliabilityof system operation are greatly improved. Compared with other defrosting control methods such as laser detection and photoelectric conversion, the defrosting control method is simple in structure, lowin cost and capable of being easily combined with an existing air source heat pump system for use and popularization.