In order to solve the problem of intermittency in solar photovoltaic power generation, an unsteady state model of the packed bed phase change heat storage tank was established, and the influence of inlet flow rate, inlet temperature and initial temperature on the heat storage process was studied by numerical simulation. The results show that increasing the inlet temperature is the most effective way to improve the heat storage power. When the inlet temperature is 363 K, the heat storage power is increased by 21.2% and 75.2% respectively compared with that of 353 and 343 K. The increase of inlet flow rate does not change the total amount of heat storage, but results in a higher heat storage power and an increase in the thickness of the thermocline. The heat storage power at the inlet flow rate of 0.001 m/s is 20.4% and 64.8% higher than that of 0.0008 and 0.0006 m/s, respectively. The heat storage power at an initial temperature of 290 K is 6.2% and 12.7% higher than that of 295 K and 300 K, respectively, but the initial temperature has few effects on the thickness of the thermocline.