Objective (1) To investigate the effect of the extended distance of the arms of shape memory alloysawtooth-arm fixator(SSEF) on the embracing force of SSEF. (2)To investigate the effect of the ratio of the diameter ofthe fractured bone to the inner diameter of the SSEF on the embracing force of SSEF. Method (1)Getting a series ofsmall steel rod made of 1-Cr-13 steel with the diameter of 5mm and the length of 27 mm, 28 mm, 29 mm, 30 mm, 31 mm,32 mm, 33 mm. Getting a plane with the width of 3 mm out of each steel rod to stick the strain gages on ,pressurizing.(2)Utilizing the different pressure sensors to simulate the different bones with different diameters .Extending the free endsof the two arms to different distance and then putting SSEF in a electronic container in which the temperature can beadjusted.While the temperature of the SSEF is increasing the SSEF tends to recover its original shape , so the two armspress the pressure sensor making the steel rod get a little decrease in the length which can be measured by the YJ-35instrument. (3)Utilizing the SAS to analyze the data we got. Results (1) The SSEF’s embracing force is decreasingalong with the extended distance of the arms of SSEF increasing.(2)The embracing force is the largest with the steel roadof 32 mm inside the arms of SSEF with the diameter of 27 mm. Conclusion (1) In surgery, the free ends of the arms ofSSEF should just be extended to the distance at which it can be put on the fracture bone and try to avoid being extendedto a very large distance. (2)The diameter of SSEF=0.87×the diameter of the bone, we can refer to this formula wheneverwe have to choose a suitable size of SSEF to fix the bone fracture.