Abstract: This paper studied the edge detection algorithm of pantographslide plate, described the multi-scale wavelet edge detection algorithm at pixel level based on Canny operator and the sub-pixel edge detection algorithm based on Zernike moment. Combined with the actual pictures of Guangzhou Metro Line 13, the comparative experiment was carried out. The experimental results show that, compared with the traditional pixel level edge detection algorithm, sub-pixel level edge detection algorithm has higher accuracy, and can meet the needs of pantograph slide edge detection.