The construction defects such as scratches and stains on the main insu lation surface can easily lead to insulation faults.The construction defects ca n be intelligently controlled by using image recognition technology.To solve th e problem that it is difficult to detect scratches and stains on the main insula tion surface of 10kV cable,this paper proposed a defect recognition algorithm f or the main insulation surface of 10kV cable based on Canny operator.In this pa per,the scale-invariant feature transform (SIFT) method is firstly used to complete the stitching of the cable main insulation images to obtain a complete original image,using a gaussian filter to remove the image noise.And then the Canny operator is used to calculate the gradient and amplitude of the defect edge on the main insulation surface,suppre ss the maximum information point,remove the false edge,and get the defect edge information generated by scratches and stains.The experimental results clearly show that the edge contour of the defect image of the cable main insulation sur face detected by the Canny algorithm in this paper has higher purity and complet eness,the defect edge is clearer,and the average accuracy of the algorithm rea ches 95.42%,which verifies the effectiveness of the algorithm.