Objective To study three-dimensional finite element model of pelvis and make its stress analysis after-sacrum tumar excision. Methods By using theanalysis software-"ansys", we have established two models: the whole pelvic model and the model after- sacrum tumar excision, and compare the stresses getting from the models. Results After establishing the two models and loading on them respectively, the results were got as following:(1) In the whole pelvic model, the forcestransmittedalong theroute: lumbar→sacrum→sacroiliac joint→ilium→ischial. For each of the node, the force distribution is symmetrical with limited intensity of pressure . While in the model with sacrum tumar excision, the transmission is affected. (2) In the SF model, the forces of nodes in the sacroiliac joint and ischium are larger than that in the same nodes in the whole pelvic model,which may cause the stability of pelvic is descend and the opportunity of loss of pelvic integrality is ascend. Conclusion By establishment of pelvic three-dimensional finite element model after- excision of sacrum tumar and its stress analysis comparing with the whole pelvic model, it is proved that its stability has been changed.