高功率固体激光装置主放大器是能量提取最多的一个环节，它受环境影响因素较多，难以建立考虑各因素影响的微观模型。目前，国内外还没有主放大器增益的精确预测模型和实验数据分析报道，现有预测模型较为粗糙。从统计角度对高功率激光装置主放大器增益的变换规律进行了分析，指出宏观上3种不同特点的增益变化，分别为增益的低频演化规律、增益随日运行发次的变化规律及增益的高频稳定性特性；并由此建立了包含权重因子的主放输出预测模型。通过神光Ⅲ原型装置的运行数据对建立的模型进行了考核，结果显示，与以往的单一发次的递推模型相比，新模型对增益预测的准确性可提高1倍。研究结果对大型固体激光装置的高效运行具有指导意义。

Output energy of high power laser facility is mostly extracted from main amplifiers. Due to the circumstance complexity and diversity in paractice, it is difficult to build a precise microcosmic model in consideration of various factors. However, the existing predicting model of gain is imprecise, and no accurate model and corresponding experimental results are reported so far. Statistical methods are proposed to analyze the gain stability of main amplifiers in high power laser facility. The varying rules of the gain are put forward, including low frequency change, variation by the sequence number in one day and high frequency stability. Based on above-mentioned rules, the gain prediction model with weight factor is built and verified by SG-Ⅲ prototype operation data. The results show that the accuracy of gain prediction can be improved by one time in comparison with that of the old method, giving powerful directions for efficient operations in high power solid laser facility.