Objective This study aims at comparing and optimizing postoperative stability and biomechanical compatibility in treating different types of vertically unstable sacrum fractures by using percutaneous posterior-ring tension-band steel plate and percutaneous iliosacral screw. MethodUsing CT and MR images of the second generation of Chinese digitized human “male No. 23”, the finite element models were developed respectively for two groups of vertical sacrum fractures of Denis Ⅰ,Ⅱ,Ⅲ zone with ipsilateral superior and inferior pubis ramus fractures treated with percutaneous posterior-ring tension-band steel plate (P-group) vs percutaneous iliosacral screw (S-group). The multi-solution finite element analysis and experiment validations were adopted on the basis of lumbosacral spinal three-column loading modes and sacroiliac joint physiologic behaviour. Results When simulating vertical sacrum fractures of Denis Ⅰ zone, von Mises stresses of internal fixation device of posterior and anterior rings of P-group were significantly increased, while the sacrum displacements were also increased compared to those in S-group. Whereas as simulating vertical sacrum fractures in Denis Ⅱand Ⅲ zones, von Mises stresses of fixator of both rings in P-group were lower than those of S-group, and the sacrum displacements were also remarkably decreased. Conclusions Considering internal fixation stability, mechanical compatibility for fracture healing and surgical procedure security, percutaneous iliosacral screw is more appropriate for the treatment of vertically unstable pelvis fractures with sacrum Ⅰzone injury, whereas percutaneous posterior tension-band steel plate is in favor of the treatment of vertically unstable pelvis fractures with sacrum Ⅱ and Ⅲ zone injuries.