The edge detection algorithm based on sub-pixel can effectively improve the positioning accuracy of contour edges, but the quantitative evaluation method of sub-pixel positioning accuracy needs to be further studied. In this paper, a subpixel edge detection methodology supported by Zernike moment is initial analyzed. A triangle-based simulation method and a calibration-plate–based experiment method are proposed to judge the accuracy of the subpixel algorithm. The findings indicate that the proposed simulation method can quickly and quantitatively evaluate the accuracy of the sub-pixel detection algorithm. The effectiveness of the sub-pixel detection algorithm in improving the accuracy of edge detection is also verified.