介绍了小镜法准直正支共焦非稳腔的原理、方法和步骤，并将它与传统使用的几种方法进行了比较。实验分析结果表明：小镜法除兼容其它方法的优越性外，还特别适合于需要确定强激光束远场焦点位置的场合 This paper introduces the principle, method and steps of the small mirror method to collimate the positive branch with the confocal lumen and compares it with the traditional methods. Experimental results show that: the small mirror method in addition to compatibility with other advantages of the method, but also particularly suitable for the need to determine the strong laser beam far field focus position