Objective To investigate the validity of screw-rod system for fixing pelvic fractures by comparing the biomechanical behaviors from using screw-rod system or steel plate for fixing Tile B2 type pelvic fractures. Methods The finite element models of normal pelvis including ligaments, and Tile B2 fractured pelvis fixed by different screw-rod fixations (2 screws at fractured side, 3 screws at fractured side and at healthy side), and steel plate fixation were established. The vertical load (500 N) was applied on the upper terminal plate of the first body of the sacrum to simulate pelvis load during double-leg standing, single-leg standing and sitting. The displacement and stress distributions on normal pelvis and fractured pelvis with screw-rod fixation or with steel plate fixation were compared and analyzed. Results Both the screw-rod system and steel plate could effectively fix the fractured pelvis, and the fixation models showed similar displacement and stress distribution as normal pelvis. The largest displacement of fractured pelvis with 3-screw fixation on the diseased side was smallest under each working condition, and its stress level was also obviously lower than that of the other internal fixation models. During double-leg standing, compared with 2 screws fixation, 3 screws at healthy side fixation, and steel plate fixation, the Von Mises stress for 3 screws at fractured side fixation was reduced by 30.4%, 20.8%, 20.3%; during single-leg standing, the Von Mises stress for 3 screws at fractured side fixation was reduced by 31.8%,25.4%,18.5%; during sitting, the Von Mises stress for 3 screws at fractured side fixation is reduced by -6.5%,28.0%,61.1%,respectively. Conclusions The screw-rod system can fix Tile B2 pelvic fracture effectively, especially for 3-screw fixation on the fractured side. The results can provide the theory basis for clinical treatment of pelvic fracture.