In this paper,the kinoform of a specific snowflake pattern is designed,the original size of the input image is set to be10mm×10mm,according to the sampling theorem of designing diffraction optical element,the numerical calculation is needed,and that the sample interval and the number of sampling points of the input plane and output plane could be determined as1508×1508 for the number of sampling points and 6.63μm for the sample interval.The iterative Fourier transform algorithm is used to calculate the kinoform of the snowflake pattern,the reconstructed image is simulated by computer,the size of the kinoform and the phase structure are obtained.