In order to improve the calibration accuracy, a method of automatically and accurately extracting the center of the circular marker point is proposed by the paper, and the research of camera calibration is carried out. Firstly, the calibration image is preprocessed, and then the center of four circular markers on the calibration board are automatically extracted by the program to perform image correction. Secondly, an automatic iterative projection method is applied to iteratively process the corrected image, and finally the center coordinates of the mark point on the original calibration image are obtained through anti-perspective projection. Two extraction methods including manual and automatic are designed. The center coordinates of the last extracted mark points are substituted into Zhang Zhengyou's calibration algorithm, and the tangential distortion is considered to obtain the calibration parameters of the camera. The experimental results show that as the number of iterations increases, the reprojection error becomes larger and larger. When the number of iterations is one, the accuracy of calibration is better than that of multiple iterations, and it is slightly higher than the accuracy of manual extraction. Compared with the 0.2pixel calibration standard of Microvision commercial software, the accuracy has been improved by about 58%.