The auto insulator defect recognition method is more efficient and reliable than manual method, and it has lots of application. The paper presents an insulator recognition method, and meanwhile it attempts to explore the intrinsic characteristics among different images. Then, based on that many transformations of the image have the structure of matrix Lie group;the paper proposes a method that can recognize the defect of insulator using the Lie group method. The simulation results show the effective of the method.