Abstract: At present, there were few research on the evaluation of uncertainty of mechanical measurement results for metal structures, however the evaluation of uncertainty could evaluate the reliability of mechanical measurement results of structural members. The connecting shaft of rotor body was loaded by universal tensile testing machine on axial, and the maximum strain on connecting shaft was measured when the load was 80 kN. The influence factors of measurement and the evaluation of uncertainty were analyzed. The results show that the expanded uncertainty on strain measurement results of the connecting shaft of rotor body was 28 με. The standard value given by standard analog strain calibrator, measurement repeatability, accuracy of tensile equipment, strain gauge grade, conductor resistance and ambient temperature had great influence on the accuracy of measurement results, among which the accuracy of tensile equipment and strain gauge grade had the greatest influence.