Abstract: In this paper, a method based on wavelet analysis is evaluated for detection of defects in the Tokamak vacuum vessel shell structure. First, ratios of dynamic strain energy change under transient electromagnetic force before and after structure damage are extracted, and then they are analyzed by using Sym4, DB4, Mexh and Haar wavelet functions of different scale factor to evaluate the position and size of the defects. Second, a comparison of recognition accuracy of different wavelet functions and scale factors are conducted. The numerical simulation results show that, position and size of defect in the vacuum vessel structure can be efficiently evaluated from strain energy change ratio with the proposed wavelet method by selecting proper wavelet base function and scale factor.