In this paper, the mechanical properties of supracondylar part of humerus were studied with the experimental methods of two dimensional photoelasticity and three dimensional finite element analyse. The results showed that' O In the supinator position,there was conpressive stress in the medial side, while there was tensile stress in the lateral side. In the pronator and neutral position, the result was contrary to it. @The shearing stress in supinator, pronator and neutral position didn' t change much. ③In the supinator position, there was medial displacement in the medial and lateral sides. In the prnator and neutral position, the result was contrary to it, but the displacement hadn' t significat difference in both sides. Integrating with Salterl's theory, the authors suggest the rational fixation methods for the fractures of supracondyle of humerus.