In order to simulate the mechanical behavior of the human body during walking，the multiple-rigid-body model was used to simplify the human bipedal walking behavior，and a four-rigid body，four-degrees-of-freedom human body dynamic model was established. The dynamic equation of motion during the swing phase of the dynamic system was derived using Euler-Lagrange equation. In order to mimic the real human locomotion behavior，the Bézier curve was used to plan the trajectory of the driving degree-of-freedom，and the multiple degrees-of-freedom equations of motion was simplified into a single degree-of-freedom system which was solved as a boundary value problem. The numerical simulation results were compared with the actual test and the load model，reasonable feasibility was verified.