Abstract: The contact/impact problem of the multibody system dynamics is a typical boundary nonlinear problem, which faces a huge numerical difficulty in dynamic simulation. The efficiency of numerical calculation is seriously affected for the necessity of constant and complex contact detection in the solving process. In order to solve the contact/impact problem of the multibody system dynamics quickly, an improved algorithm for the contact/impact problem of multibody system dynamics is proposed based on the signed distance field in this paper. The shortest distance and normal vector of any point from the object surface are solved by performing trilinear interpolation on the pre-generated signed distance field. The contact detection is divided into two essential processes: global detection and local detection. At first, the bounding box called OBB is used to quickly judge whether there is a potential contact between objects in global detection. Then, a contact detection algorithm is further optimized based on the information of signed distance field and octree structure in local detection. In addition, the Hertz contact force model and Coulomb friction force model based on velocity are used to establish the discontinuous dynamics equations of the multibody system. Finally, the correctness and high efficiency of the proposed method in solving the complex impact dynamics problem of multibody system are verified by the successful simulation of typical calculation examples and an engineering case of spacecraft rendezvous and docking. The proposed method can be further extended to study the contact/impact dynamics between rigid bodies with complex configurations and flexible bodies.