A method of amplitude fitting is proposed to solve the degeneration problem of the quality of binary images reconstructed by kinoforms. By fitting a small amplitude to the zero-amplitude area of the binary image, involvement of phase in this area during the iteration is ensured. As a result, the degree of freedom during the design of kinoform is increased, and the quality of the binary image reconstructed is improved. Quantitative analyses and discussions of the improved result are given by comparing the final simulation results.