When an ASHP unit operates in heating mode, frost can be accumulated on the surface of its outdoor coil. Currently the most widely used defrosting method for ASHPs is reverse cycle defrost. However, the fundamental problem for such a method is that there is insufficient heat available for ASHPs during defrosting. This paper reports on an experimental study of developing a novel reverse-defrosting method which was thermal energy storage (TES) based on using phase change material (PCM). Comparative experiments were carried out at two operating conditions: standard defrosting condition and the PCM-based defrosting condition. Results indicated that the use of this PCM-based reverse defrosting method could help shorten defrosting time, increase defrost $COP_d$, enhance system reliability, reduce transition duration from defrost to normal space heating operation, and improve indoor thermal comfort for occupants during defrosting and heating resumption process while without degrading the quality of space heating provided by the ASHP during heat operation.