在增益导引的作用下，未采用任何补偿措施，主振荡功率放大（MOPA）激光器的输出光光束质量得到改善。综合考虑热效应、增益导引效应、增益饱和效应后，在MOPA系统中建立了一种新的激光放大模型，并进行了数值计算，模拟结果与已报道的实验结果符合较好。另外，计算结果表明填充因子和抽运光功率是影响输出激光光束质量的重要因素，而热效应与增益导引效应是其深层原因，这对进一步利用增益导引效应改善光束质量具有指导意义。

With the help of gain guiding effect, the quality of the beam which emitted from master oscillator power amplifier (MOPA) laser system can be improved without any compensations. Considering thermal effect, gain guiding effect and gain saturation effect comprehensively, a novel model for laser amplifier in MOPA system is developed and numerically caculated. The simulation result approximately agrees with the recently reported experimental counterpart. Moreover, the simulation result reveals that fill factor and pump power are two key aspects influencing the final beam quality of the MOPA system. Besides, the thermal effect and gain guiding effect are the underlying reasons. This analysis is meaningful for improving beam quality of laser emitted from amplifier.