There are certain disadvantages in several conventional defrosting methods for cascade air source heat pumps. For this reason, an energy storage defrosting method for cascade air source heat pumps was proposed. In order to study its low temperature adaptability, six different outdoor simulated conditions were designed by changing the ambient temperature, relative humidity of outdoor side and frosting time. The characteristics of the energy storage defrosting mode under these six conditions were experimentally studied. The experimental results indicate that, the defrosting durations under six conditions are within the range of 520~770 s, the system operates normally under each working condition, the system defrosting performance is stable and the average indoor heating capacity can reach more than 57.4% of the normal heating capacity. The results show that the system has good low temperature adaptability.