针对基于微透镜阵的光纤激光外腔谱组束系统的光束质量评价问题，利用高斯光束的传输变换理论，建立了评价谱组束激光光束质量的理论模型。通过数值模拟，详细分析了各相关参数对谱组束光束质量的影响，结果表明：在基于微透镜阵的谱组束系统中，离焦量、微透镜焦距及模场半径是影响谱组束激光光束质量的主要因素；阵列宽度对谱组束激光光束质量影响较小，阵列宽度由 0增大至 10 mm过程中，x方向和 y方向的光束质量因子分别保持在 1.225和 1附近，与传统谱组束系统相比，组束激光的光束质量得到明显改善；为了保证 x方向的光束质量因子小于 1.3，必须把离焦量控制在 -0.017~0.017 mm范围内，对于采用大模面积双包层光纤的组束系统，可通过适当增大微透镜阵焦距的办法改善组束激光光束质量。

Aiming at the problem of beam quality evaluation for external cavity-based spectral beam combining system with microlens array, the theoretical model for evaluating the beam quality of beam-combined laser is established. According to the model, the influences of relevant system parameters on beam quality are numerically analyzed in detail. The simulation results show that the beam quality is mainly influenced by the defocus value, the focal length of microlens and the mode field radius, while the influences of the array width are little. With the array width changing from zero to 10mm, the beam quality factors in x and y directions are preserved near 1.225 and 1 respectively. Compared with the traditional spectral beam combining system, the incorporation of microlens array effectively improves the beam quality of output laser. In order to keep the beam quality factor in x direction smaller than 1.3, the defocus value ought to be restricted in a range of -0.017~0.017 mm. For spectral beam combining system with large mode area double-clad fibers, the beam quality can be improved through utilizing microlens array with longer focal length.