Based on the three-dimensional rotating coordinate mathematical model, this paper has established the mathematical equations for the principal moments of inertia, the centroid position and the center of gravity position. In order to validate the validity and reliability of this mathematical equation model, the paper designs the three-dimensional virtual simulation system of changes in the center of gravity during the process of computer tennis player. And it analyzes the performance of this system through the prediction of the center of gravity position of athletes. Through the computer GMM technology, we carry out the probability and statistics for the boundary of gravity position path and have obtained the GMM gravity statistical plane distribution map and three-dimensional distribution map. According to the distribution map, we obtain the change table of the gravity and the centroid position. It has been introduced to guide the movement training of tennis players, which has provided technical reference for tennis players training.