Objective To investigate the biomechanical differences of three internal fixation approaches, namely improved Galveston (IG), reconstruction plate (RP), and il iosacral screw (LS) to the posterior pelvic ring fracture dislocation and provide experimental evidence for the cl inical appl ication of proper internal fixation method. Methods Six donatedfresh adult cadaver pelvic specimens (age averaged 45 years old) were numbered randomly and their normal biomechanics were tested by the measure instrument (MTS855 Mini-Blonix). The displacement values of normal pelvis were measured under the vertical compression (800 N) and reverse direction compression (8 N·m). Then they were made into left Denis I pelvic fracture and fixed with the IG, RP, and LS, respectively, in different orders. Biomechanics test was conducted on the fixed pelvis from both the vertical and the reversed directions. Results Concerning the direction of vertical ity and torsion, the order of fracture displacement from small to large was the normal pelvis, LS, IG and RP. There was no significant difference between LS and the normal pelvis (P gt; 0.05), and the differences between other tow groups were significant (P lt; 0.05). Conclusion The LS fixation can provide better stabil ity for posterior pelvic ring fracture dislocation when compared with IG and RP.