The structure of 120 MN bridge bearing testing machine was researched more comprehensively by ANSYS, moreover, stress and deformation of the frame under preload and center load condition were also analyzed. The  research results are as follows: this program of the testing machine improves the stress concentration greatly,the frame and its different parts have smaller deformation, which meets the design requirements.The law of beam height and plate thickness about how to impact on the structure was found through investigating two chief factors which could  impact frame‘s performance, and on this basis, the original structure was also optimized relevantly to obtain a kind of more economical design program.