Objective Creating a 3D finite element model of a full pelvis with sacroiliac joint fracture. Comparing the biomechanical properties of the model where the fracture part was fixated by using a new sacroliliac anatomy type Bar-plate internal fixation system to iliosacral screw fixation and front reconstruction plate fixation. Methods A specially designed biomechanical semi-automatic mesh generator was employed to generate the complete pelvis finite element model from CT datas. Then, one side of sacroiliac joint related ligaments was deleted to simulate the case of sacroiliac joint fracture. Using a new sacroliliac bar-plate internal fixation system with anatomic plate (SABP) to fix the fracture part, and the comparing models using iliosacral screw fixation (SS) and front reconstruction plate fixation (SP) were also generated. Finally, all models were simulated under same loading conditions. Results Using SABP fixation, the maximal displayment of the sacroiliac joint decreases about 40% and 42% compared to SS fixation and SP fixation, respectively. The minimal value of maximal stress for main loading transfer regions was reached by SABP fixation and t he maximal stress of SABP decreases about 33%-70% compares to SS in regions of fracture hip cortical bone and cartilages bone, and decreases about 60%-75% to SP in regions of sacral cortical bone and fracture hip cortical bone. Conclusion The new sacroliliac anatomy type Bar-plate internal fixation system has better biomechanical properties than other internal fixations, and deserves to be put into clinical application.