通过求解四能级系统的半经典密度矩阵方程，用迭代法计算了CO2-10R(6)泵浦小型超辐射光泵NH3分子远红外激光器(mini-NH3-OPFIRL)的P支和Q支跃迁输出光强的增量比。计算表明在超辐射小型NH3光泵远红外激光器中，V2:a→ｓP(5，4)和a→sQ(5，4)模式竞争结果，Q支跃迁占优势，使P支被抑制。理论计算与实验结果一致。

The semiclassical density matrix equation of four energy levels was solved. Then by means of iteration method, the output power increment ratio of V 2∶a→s P(5, 4) to a→s Q(5, 4) transition in miniature optically pumped NH 3 molecules far infrared superradiant laser (mini NH 3 OPFIRL), which was pumped by CO 2 10R(6) line, was calculated. The calculation showed that the mode competition between the V 2∶a→s P(5, 4) and V 2∶a→s Q(5, 4) in superradiant mini NH 3 OPFIRL led to the elimination of V2:a→s P(5，4) and V2:a→s S(5，4) in superradiant mini-NH3-OPFIRL led to the elimination of V2:a→s P(5，4) transition branch. The theoretical calculation was consistent with the experimental result.