在激光等离子体典型参数条件下，利用磁撞－辐射模型计算了类锂硅离子５ｆ－３ｄ和４ｆ－３ｄ跃迁的粒子数反转比率和激光增益系数。讨论了不同热带条件和不同冷却速度下，激光增益系数的变化。计算结果表明，高功率、短脉冲激光产生的高温等离子体在快速冷却条件下能产生软Ｘ射线激光增益。 Under the typical parameters of laser plasma, the particle inversion ratio and laser gain coefficient of 5f-3d and 4f-3d transitions of lithium-like silicon ions were calculated by using the magnetic collision-radiation model. The changes of laser gain coefficient under different tropical conditions and different cooling rates were discussed. The calculated results show that the high-temperature, high-power, short-pulse laser produces a soft X-ray laser gain under rapid cooling conditions.