In computer vision system, the corners position need to be extracted from plane plate image. This paper presented a novel algorithm that improved the accuracy of corner detection from pixel to sub-pixel. The Canny operator was used to detect the corner edge pixels, and Gaussian filter was substituted by the bilateral filtering. It can remove noise and retain more slight edge information. Then, the corner edge pixels were transformed by Zernike moment and the sub-pixel edges of the corner were getted. Finally these sub-pixel edge points were linearly fitted and it was resulted in the corner coordinates of the intersection of two fitting straight lines. The experimental results show that the proposed method improves the corner detection precision to 0.1 pixel.