Based on ANSYS ICEM software, the physical modeling and grid division of air-cooled heat pump unit were conducted. Under normal working condition, the temperature field and velocity field of running unit were simulated by using Fluent software, and the heat dissipation process was analyzed. Aiming at the problem of low heat dissipation efficiency of air-cooled heat pump unit due to high temperature in summer, an auxiliary heat dissipation system was designed and its structure was optimized. The water curtain pre-cooling and atomizing spray devices were used to strengthen the heat exchange process, improve the heat dissipation efficiency and reduce the heat dissipation dead zone. The effects of different auxiliary devices on the heat dissipation performance of the units were tested through experiments. The results show that adding auxiliary cooling system can effectively improve the cooling efficiency of the unit. Under the same outdoor air condition, the atomizing spray device exhibits more advantages than the water curtain precooling device in heat dissipation performance and evaporation efficiency of the unit.