Objective Two-rigid-body system of human upper extremity was founded with some proper simplification on the analysis of the physiological structure and motion characteristics of the upper extremity structure. The motions of such upper extremity were analyzed. Methods Using ADAMS simulation software, the upper arm and the forearm were simplified as two rigid-bodies, the conjunction between the upper arm and the trunk as a spherical joint, the conjunction between the upper arm and the forearm as a revolute joint, and muscular actions as forces acted on the mass centers of the upper arm and the forearm. Thus, motion models for human upper extremity were founded and simulation were carried out on the three simple motions for abduction/adduction, inner rotation/outer rotation and flexion/extension. Results The model simulation is coincided with the practical motion of human upper extremity. Conclusion Motion model of human upper extremity may be well founded by using ADAMS to analyze the motion of human upper extremity.