An optical system of pin-hole objective lens with large field is designed with relative aperture of 1/5, focus length of 5 mm and field angle of 125°. In this structure, the modulation transfer function for all fields is bigger than 0.5 at 50 lp/mm, and the imaging reaches the diffraction limit, but the full field distortion rate reaches -46%. According to optical imaging theory and image processing technology, the lattice template is used to calculate the optical center and the distortion coefficient. The distortion correction model is built and distortion correction algorithm is designed. With a combination of linear imaging model and distortion correction model, the calibration equation of distortion correction rate is built. The distortion correction rate obtained by this algorithm is 96.17%. This calibration method is compared with other methods, and we find that the proposed method is simple and practicable. The proposed method basically meets the needs of industry, and it can be widely used in image distortion correction of large field lenses.