The traditional small univalue segment assimilating nucleus (SUSAN) operator may confuse the corner and the edge. An improved SUSAN subpixel operator with high speed and high position accuracy was proposed. According to the characteristics of the SUSAN template, the gray symmetry degree was defined to distinguish the corner from the edge. Sobel operator and gray square centrobaric arithmetic were synthesized with the improved SUSAN operator in subpixel corner detection. In the camera calibration experiments, this method proved to be rapid and efficient, and the improved operator’s average reprojection error was less than 0.2 pixels.