The necessity of computational multi-body dynamics simulating the astronaut extra vehicular activity (EVA) was described. The 4 joints universal human body inverse kinematics model and inverse dynamics model in weightlessness utilizing computational multi-body dynamics were proposed. A typical EVA, an actual large-mass-handling EVA performed on STS-63, was chosen as the instance to simulate. Based on some simplifications, a typical EVA was simulated and calculated using universal human model. Considering the influence of weightlessness on human modeling, the universal model should be amended. The results were analyzed according to energy comparison method. The results showed when hand movement contrail radius and angle velocity minishing, movement time prolonging and hip joint flexion moving, accomplishing task retrenched energy. Human body joint movement comfortable scope could be achieved by energy comparison method. The calculational methods provided the reference value for the astronaut intra and extra vehicular activity simulation and ergonomic analysis.