It is conducive to understand the movement of the dummy, the analysis of dummy injury curves and restraint system matching by studying on the trajectory of dummies. By viewing the crash video is difficult to quantitative analysis of dummy motion, so how to get the dummy trajectory through the test data is the urgent thing to solve the problem for engineers. This paper studied the relationship between the pelvis rotation angle and the pelvis acceleration based on the restraint system simulation model and the vehicle test data, used mathematical analysis method to conclude the mathematical formula, and summarized the method that dummy pelvis acceleration transforms into pelvis trajectory. This method provided the basis and foundation for the matching and parameter optimization of restraint system.