In order to optimize the heat storage performance of the single-tank molten salt heat storage system, the influence law of setting moving baffles in the storage tank on the heat storage process was discussed. The influence of the moving baffle on the heat transfer of molten salt flow in the tank was studied by numerical simulation method. The dynamic movement of the baffle was simulated based on the dynamic grid and grid adaptive technology. The heat storage processes before and after the setting of the baffle were compared, and the influence of the moving baffle on the heat transfer of the heat storage fluid flow was analyzed. On this basis, the influence of the moving speed and size of the moving baffle on the heat storage performance of the system was further discussed. The results show that the moving baffle can promote the flow heat transfer of molten salt and enhance the heat storage capacity of the tank compared with the case without baffle. The size of the baffle has a little effect on the heat storage process, while the moving speed of the baffle has a significant effect on it. Within the range of parameters studied, the thermal storage time of the system can be reduced by up to 17.65% with the addition of the baffle, and the thermal storage efficiency can be increased by up to 11.65%. Further results found that the heat transfer of molten salt can be promoted when the moving baffle is always above the thermocline, while it is weakened when it is below the thermocline. Therefore, setting up moving baffles in the storage tank is an effective way to improve the performance of the molten salt heat storage system. The speed of the baffles and their positional relationship with the thermocline are the key factors affecting the heat storage efficiency.