激光陀螺光路稳定性决定着陀螺的性能，而谐振腔内外压差是影响陀螺光路稳定性重要因素之一.为了研究腔内低气压对激光陀螺光路变动及其损耗的影响，采用ANSYS仿真软件对激光陀螺在腔内低气压状态下反射镜的微小形变进行了仿真计算，结果表明: 低气压状态下，反射镜的中心发生最大形变，其中球面镜最大形变量为545 nm,平面镜最大形变量为31 nm，这不仅引起光路偏离光阑中心390 nm，同时引起球面镜曲率变化174 mm.进一步从理论上分析了这种变化对光路变形和谐振腔损耗的影响，结果表明: 上述变化综合引起谐振腔损耗变化2%~3%，其中球面镜曲率半径的变化是引起损耗变化的主要原因，增加球面镜槽深或降低腔内外压差都能有效减小这种光路的变化.通过搭建光路测试系统，进一步验证了计算结果的正确性.

The light path stability of ring laser gyro determines its performance, while the internal and external pressure difference of resonator is one of the important factors influencing the light path stability of gyro. To study the low air pressure assembly causing light path variations and the loss changes of ring laser gyro, the micro-deformation of mirrors was simulated and calculated by ANSYS software. The results indicate that under the condition of the low air pressure, there is maximum-deformation in the center of the mirror, therein to, the maximum-deformation of spherical mirror is 545 nm, and the maximum-deformation of plane mirror is 31 nm, thus this deformation leads to the light path′s deviation of 390 nm from the center of diaphragm and brings out a curvature variation of 174 mm for the spherical mirror. Furthermore, the deformation influence on the light path variation and the loss changes of ring laser gyro is calculated in theory,the results show that this deformation synthetically cause about 2%~3% loss variation of resonator, among them the variation of curvature is the main cause of loss variation. To increase the groove depth or decrease the air difference between outer and inner of the resonator will effectively reduce the light path variation. A test system is built and verifies that the results of calculation are correct.