The current experimental methods, such as the motion capture system, high-speed video, plane photography and surface EMG, cannot show the details of the muscle strength, or explain the nerve-muscle coordination mechanism during human motion. Thus, computer modeling and simulation are developed and become a new method for researchers in China to study human motion, and the software LifeMOD, AnyBody, ANSYS are mainly used even if these softwares have some limitations such as less precise muscle control and relatively higher prices. Developed by Stanford University, OpenSim is an open-source platform for muscle model development, simulation and analysis of neuromuscular system based on C++ and Java. In this paper, on the basis of computer modeling and mathematics theoretical derivation, the OpenSim modeling theory and simulation steps were introduced in detail to provide some theoretical references for researches on sport biomechanics. The future research directions by using OpenSim modeling simulation to study neuromuscular mechanism of the hemiplegic gait and Parkinson gait, and to improve and perfect the rehabilitation ways of the abnormal gait were also discussed.