Abstract: This paper presented an energy storage air source heat pump system which can heat and defrost quickly. The experimental test was carried out in the outdoor conditions of-0.7 °C and 95% relative humidity. The results show that in the process of frosting,the heat accumulator can effectively prevent the air temperature falling of the indoor unit. In the process of defrosting,the compressor of the new system has great output and high efficiency. When using the new system,defrosting duration was shortened by 68%,and defrosting energy consumption reduced by 51.4%. The indoor air temperature is 28 °C at the end of the defrosting,which is 22 °C higher than that of the conventional system,bringing about no cold feeling during the defrosting. The effect of the quick heating after turning on the unit is very considerable,the heating amount of 6 minutes for the new system is about equivalent to that of 10 minutes for conventional system. Therefore,the new system proposed greatly improves the heating effect of air source heat pumps.