Liquid sloshing is a very complex phenomenon with large free surface deformation and strong nonlinear characteristics, which may bring danger to the safety of the structure. On one hand, the violently sloshing will exert large slamming pressure on the bulkhead, leading to the deformation even the damage of the structure. On the other hand, the liquid sloshing will stimulate the motion of the tank causing dynamic instability. Therefore, it is of great significance to study the liquid sloshing. In this paper, the inner-house solver based on MPS method MLParticle-SJTU is used to simulate the liquid sloshing phenomenon inside a spherical tank according to the design requirements of aerospace vehicle. Considering h/R=0.2~1.8 six groups of different liquid filling rates, apply initial excitation to the tank and allow it to decay freely. The natural frequencies and damping of different filling rates are calculated respectively. The results show that with the increase of water depth, the natural frequency of liquid sloshing increases, and the damping coefficient decreases.