对于采用离轴多程放大技术的高功率激光装置，抑制其自激振荡的技术具有重大研究价值。针对工程中发现的主放大系统小孔板附近结构表面比较光亮，当腔内放大器工作时，在增益足够条件下，光亮结构面和腔镜间形成谐振腔而产生自激振荡，烧蚀腔内器件的问题，基于蒙特卡洛方法模拟结构表面，依据几何光学原理推导了激光光束在结构表面反射模型，采用该模型代入工程中光路部分参数计算了主放大系统结构表面粗糙处理工艺和反射进入放大器内份额的关系，并将该表面处理工艺应用于工程中，通过增大结构表面粗糙度，使形成的谐振腔损耗大于增益，为抑制高功率激光装置主放大系统自激振荡提供了依据。

For high-power laser devices using off-axis multi-pass amplification technology, the technology to suppress self-oscillation is of great research value. It is found in engineering practice that the surface of the structure near the aperture of the main amplification system is relatively bright, thus when the amplifier is working, with sufficient gain, a resonant cavity is formed between the bright structural surface and the cavity mirror to generate self-oscillation and ablation. In this paper, this problem of the device is studied by using Monte Carlo method to simulate the surface of the structure. According to the principle of geometric optics, the reflection model of the laser beam on the surface of the structure is derived. The surface of the main amplification system is simulated using this model, and the parameters of the optical path are used to calculate the relationship between surface roughness and residual reflected light reflected into the amplifier. The surface treatment process is applied to our project. By increasing the surface roughness of the structure, the resonant cavity loss is greater than the gain, which provides a basis for suppressing the self-oscillation of the main amplification system of high-power laser devices.