Abstract: Taking the packed bed phase-change thermal storage tank as the research object, a local non-thermal equilibrium model of porous medium was established without mesh discretization of each encapsulated particle., by using the binary nitrate composing of 60%NaNO₃ and 40%KNO₃ as the heat transfer fluid, and the mixed molten salt of 59.98%MgCl₂, 20.42%KCl and 19.6%NaCl as the phase-change material. The heat storage performance of packed bed phase-change thermal storage tank was numerically studied, and the influence of turbulence and particle structure on heat storage performance of the thermal storage tank was analyzed. To improve the heat storage performance of thermal storage tank, non-uniform particle distribution was adopted and compared with the uniform particle distribution. Results show that compared with the uniform particle diameter of 0.025 m and 0.015 m, the complete melting duration of phase-change material with the particle diameter of 0.025 m at the upper end and 0.015 m at the lower end decreases by 3.81% and 1.90%, respectively.