A novel straight through vacuum solar energy collector with molten salt phase change thermal storage layer was proposed. Solar salt (60% NaNO3-40% KNO3) was used as phase change materials (PCMs), and the effect of phase change material layer on the thermal performance of straight-through type vacuum solar energy collector has been studied numerically. The results show that: A 13 mm thick phase change material layer was added to the collector tube with an outer diameter of 17 mm, and the heat storage was increased by 53.57%; when the solar radiation is stopped, a constant temperature of 4min-16min is maintained, and then the temperature drops more slowly than that without addition. Molten salt phase change layer can significantly reduce the influence of solar cycle and instability on the straight-through solar vacuum collector tube.