With the development of technology, optical-experiment simulations, as a novel alternative method different from theory and experiment to explore new things, are attracting more and more attention from both scientists and teachers. There are two methods for Matlab program of the Fresnel and Fraunhofer diffraction patterns, one is diffraction integration, and the other is Fourier transform. In this paper, Fourier transformation well combined optical experiment phenomena and Matlab program. And with a lot of comparison of simulation experiments optical diffractive law was verified, which will contribute positive effect to optics teaching.