A ball joint is an important component of the automotive drive shaft system, as well the contact stress inside the ball joint is an important optimization goal in the design of ball joints. At present, the analysis of the contact stress inside the ball joint mainly focuses on the static contact stress analysis. The static contact stress analysis, however, cannot reflect the change of the contact stress inside the ball joint. In order to analyze the contact stress of the ball joint more effectively, a hybrid flexible and rigid bodies dynamics (HFRBD) model of the ball joint for studying the dynamic contact stress inside the ball joint is proposed. In the HFRBD model, the balls are regarded as the rigid body, while the cage, the inner race and the outer race are regarded as the flexible body. The contact parameters of the contact pairs in the model are determined on the basis of Hertz contact theory. Through the destruction test of the ball joint and the numerical example, the effectiveness of the HFRBD model and the method for the analysis of the dynamic contact stress inside the ball joint is verified. Based on the proposed HFRBD model, the stress distributions of the cage, the inner race and the outer race under different rotation angles are analyzed subsequently. The presented modeling and analysis methods for the dynamic contact stress inside the ball joint in this paper have an important reference for the design of a ball joint.