本文使用光学变换矩阵方法，分析了多元件谐振腔的等价腔问题。发展了等价腔的一些概念和方法，推出了在普遍情况下，等价腔各参量与原谐振腔各参量之间的解析关系，并得到了一组不变量；同时，还澄清了一些关于等价腔的错误看法和易混淆之处． In this paper, we use the optical transformation matrix method to analyze the equivalent cavity problem of the multi-element resonator. Some concepts and methods of equivalent cavities are developed. The analytical relations between the parameters of the equivalent cavities and the parameters of the original cavity are generalized and a set of invariants is obtained. In the meantime, The wrong view of the equivalent cavity and confusing place.