The unique memory function of Ni-Ti alloy makes it unique durative self-press function as the orthopaedics internal fixator devices, the durative embracing force provides a good mechanical condition for the bone healing in clinical orthopaedics. Through the special embracing force testing device and using self-designed experiment device which arms at this kind of arm-embracing Internal fixator experiment to observe the effect of the extended distance of arms on the embracing force when Ni-Ti shape memory alloy arm-embracing fixes fractures. It is researched that the state affected embracing force under the resistance effect, and fully realizes the law of embracing force’s variety. The investigation has been done to the clutching internal fixator which frequently used in clinical treatment of orthopedic and find that the embracing force increases with time and stabilizes finally, when the open end of arm-embracing internal fixator is in the equal temperature and opening under the resistive effect; it observes the character of embracing force which increasing along with the opening degree of the arms when the open end is at the same temperature and different opening degree; it also researches that the embracing force has the rule of change that it will reduce in repeated experiment at the same temperature, at the same place of the memory alloy arm-embracing clip. The research provides the instructions and references based on mechanics for clinical treatment.