在考虑可饱和吸收体受激态吸收的条件下，用拉格朗日乘数法求出了被动调Q激光器输出关键参数的解析解，给出了被动调Q激光器输出能量与输出耦合镜反射率的解析表达式，并通过数值解来优化选择被动调Q激光器可饱和吸收体的初始透过率、耦合输出镜反射率等关键性参数，计算和分析了红宝石被动调Q激光实验数据，计算结果十分接近实验的真实值，较好的说明了被动调Q激光器关键参数的优化效果。

The numerical method is used to solve the rate equations when the stimulated state absorption of saturable absorber is considered. The passively Q-switched output pulse energy as a function of the output reflectivity for several initial transmissions of the absorber is demonstrated. The output parameter is also demonstrated when the laser operates at maxim output energy. From numerical results of rate equations the output energy is estimated,and the key parameters of the the Q-switched lasers such as initial transmissions of the absorber and the output reflectivity are optimized. Finally,a Q-switched Ruby laser experiment data are analysed to illustrated the optimized results of the parameters.