A method of distortion correction based on parallel lines is presented, not only for radial distortion coefficient but also for tangential distortion coefficients. Firstly, an approximate line passing through the center is approached by anamorphic curves. The coefficient of distortion is combined with the vision process to correct an anamorphic image for the final calibration of the liner model. Secondly, the point with only tangential distortion is gained by the actual point minus radial distortion. The distances from the point with tangential distortion and the ideal point to the principal point are equivalent. The Least-squares method is used to fit lines in theory, and the coefficients of tangential distortion are gotten.