Project Description: Air-cooled heat pump air conditioning defrosting control method is one by measuring the evaporator outlet wind speed to achieve. The invention first simulates the system to obtain the relationship between the evaporation temperature and the outlet air velocity of the evaporator. And then calculate the evaporation temperature according to the wind speed measured by the wind speed sensor installed at the outlet of the evaporator. The evaporator surface temperature is obtained according to the relationship between the evaporator surface temperature and the evaporation temperature, and then the evaporator surface temperature is used to determine whether to defrost. Finally, it is determined whether to end the defrosting according to whether the outlet air velocity of the evaporator reaches the threshold during normal operation. The invention is mainly characterized in that the control method comprises the following steps of: 1) simulating an air-cooled heat pump air conditioner to establish a simulation model of an outdoor unit, an indoor unit, a compressor and a throttling element; 2) establishing a simulation model based on the pressure balance, the mass balance and the energy balance Principle, the system frosting operation simulation calculation, the evaporator evaporation temperature and evaporator outlet velocity relationship as follows: t0 = 0.1417v5-0.5463v4 +0.6173v3-0.0988v2 +0.4941v-4.9040 3) in the outdoor unit evaporation (Eg, Δtw = 1.5 ℃, tw = -3 ℃); set the time step (such as 2min) and the normal operation of Wind speed threshold (such as 1.8m / s); 5) when the air-cooled heat pump starts running, the wind speed measured by the wind speed sensor within a time step into Equation 1, the evaporation temperature t0; 6) Temperature t0 into equation 2, the evaporator surface temperature tw; 7) to determine whether the calculated evaporator surface temperature tw reaches the set value; 8) If tw reaches the set value, start defrosting; if not reached, continue running ; 9) start defrosting , When the measured wind speed v reaches a set threshold value (for example, greater than 1.9m / s), the end of defrosting, defrost or continue. Application prospects: Through such a defrost control method, not only simple and easy, but also can well save energy, to overcome the shortcomings of the traditional defrost control technology, a good control of defrost