In order to achieve the application of corneal topography instrument in clinical examination, the traditional Klyce three-dimensional reconstruction of the surface model is changed into the ray tracing method. 24 rings and 256 sub-pixel data per ring are obtained. The original assumed ellipsoid is estimated by the least squares method. The ellipsoid is corrected to obtain the most realistic corneal surface. First of all, the pixel level data information is obtained by the Canny algorithm. Then, the gray value of the data is smoothed to reduce the noise. And the gray gradient of the data is fitted 3 times to obtain the sub-pixel data. Finally, the clear images obtained by standard corneal topography are used for the three-dimensional reconstruction. By analyzing the curvature radii and diopter data obtained by both methods, the results show that the errors are less than 0.9%, and it proves that the proposed method is feasible.