Abstract: Based on the angular spectrum theory, an parameter optimization method of optical analog was deduced, which focused on the restrictive relationship between calculation parameters and the actual optical system, and it was validated by numerical calculation. By controlling the variables, the impact of sampling number and interval to detail error and contour error was studied, as well as the sampling parameters' near-field and far-field change of an optical system. The results shows that the parameters calculated from the sampling restriction obtain a more accurate simulation result, and the calculation error can be better explained; the selection of sampling number and interval is mutually conditioned, which also depends on the actual optical system.