A PV/T system faces the difficulty of high-temperature dissipation as a result of low heat-exchange efficiency and winter freezing challenges that badly influence the performance of the system and even damage the PV/T. These problems can be addressed by using of the PCM in a PV/T system. The PCM can absorb heat in the daytime to reduce the operating temperature of the PV cell, and release heat at night to prevent the system from freezing in winter. In this study, a PV/T with PCM was designed and constructed by the authors. A series of experiments were done to compare the performance of the PV/T with PCM with a normal water-pipe-based PV/T during the daytime and night respectively. Physical-mathematical models were developed to simulate the transient performance of the PV/T with PCM. The data was analyzed, compared and validated with the experimental results. The results for the daily electrical efficiencies of the PV/T with PCM and water-pipe-based PV/T are 12.1% and 11.9% respectively, while the thermal efficiencies of two systems are 42.3% and 44.5% respectively. Also, the temperature of the PV/T with PCM is obviously higher at night in winter. This shows that PCM can improve the performance of a PV/T system. The results reveal good agreements between model simulation and experimental measurement with sufficient confidence. The design parameter analysis shows that the PV/T with single melting-temperature PCM panels can hardly meet the two requirements which are cooling the collector during daytime and preventing it from freezing at night. The study also reveals that increasing the thickness of the PCM can improve the collector’s antifreeze function.