This article describes the attenuation unit of laser energy of wide range, high precision and stepless in the semi-active laser guided weapon simulation system, which consists of two prisms (different sizes), precision displacement platform，controller and grating. The optical energy regulation principle is based on Lambert law. Only by changing the material thickness which the beam passes through，the light intensity could be changed. It achieves a wide range, high accuracy, high dynamic, continuous and stepless adjustment of laser energy. Compared with the traditional laser energy regulation system, it solves these problems such as the energy dynamics of small range, unsatisfied linearity, needing to multi-stage cascade and so on, and also has a simple structure, high stability, and low processing costs. We take 1064nm laser as the experiment, gives the design scheme and its implementation process. The method plays a role in promoting this technology.