Abstract: Objective To study the biomechanical characteristics of Ni-Ti shape-memory alloy-enclosed interlocking intramedular nail Ni-Ti En for clinical application.Methods Six transverse fractures were induced in 6 fresh humeral shafts and fixed with Ni-Ti En,plate,interlocking intramedullary nail,and Ender nail,respectively.The specimens then underwent stress analysis for comparison of the bending strength,twisting force,and flexibility.Results The bending strength of Ni-Ti En was not significantly different from that of the plate and better than ender’s nail;the twisting force of the interlocking intramedullary nail was comparable with the plate,but better than Ender nail.Conclusion Ni-Ti Enpossess good biomechanical property to meet the demand of osteosynthesis,and its less stress protection,freedom of distant nail locking,flexibility and stable fixation may accelerate fracture healing.