In order to research the water-entry impact characteristics of the sphere and further study the similarity criteria and parameter influences, the numerical simulation of rigid sphere water-entry impact is carried out using CFD method and overset grid technology. The water-entry impact characteristics of spherical structure with different ratios are analyzed under different entry angles and entry velocities. The results show that: using the control variable method, within certain range of parameters, the peak value of water-entry impact load is proportional to the 2th power of sphere radius, the 1.5th power of entry velocity and the 0.6th power of entry angle; in the coupled analysis of mass and entry velocity, the peak of water-entry impact load is approximately proportional to the product of the 1.5th power of entry velocity and the 0.5th power of the mass. The research results can provide references for model test research, and provide a few rules for calculating real data from model data.