Abstract: Based on continuous heating air source heat pump hot gas bypass defrost technology,this study proposes a segmental defrosting continuous heating air source heat pump system and investigates its performance in an enthalpy difference lab. The results show that lower ambient temperature or lower relative humidity or higher condensing temperature will reduce the average heating capacity of the segmental defrosting system. The change of compressor suction pressure in the process of segmental defrosting is 698.5 kPa smaller than that of reverse cycle defrost,and the change of discharge pressure is 238.9 kPa smaller than that of reverse cycle defrost. The defrosting sequence from top to down takes more time for each coil,while the defrosting sequence from down to top takes basically the same time for each coil,top to down defrosting sequence reduces total defrosting time by 55 s compared to top to down defrosting sequence,but has an impact on“secondary frosting”. Compared with the traditional reverse cycle defrost system,the segmental defrosting system has the advantages of short defrosting time and continuous heating,high COP,and less impact on the system. The switching of valves during defrosting will cause some local pressure fluctuations and energy loss in this system,which needs to be further optimized.