Abstract: In order to study effect of substrate on the focusing laser field in atom lithograph, based on geometrical optics and numerical simulation, effects of substrate surface slope on optical potential were studied. The results indicate that when the substrate surface has positive slope related to the laser standing wave axis, there is an area without light illumination on the surface whose optical potential is zero, and the curve of optical potential in z direction will suddenly vanish; when the substrate surface has negative slope related to the laser standing wave axis, all the surface will be illuminated by the laser and the curve of optical potential in z direction will vary smoothly to zero, and the optical potential will be symmetric related to z=0. The results are useful for the experiment of laser-focusing atom deposition.