本文讨论了n+3及n+4相多体系封闭网图的某些性质,提出了n+k(k≥3)相多体系双变度组合特征稳定多边形定理,说明:任何n+k(k≥3)相多体系的一个双变度组合,最大可在封闭网图的一个无对角线的k边形中稳定,最小可在一个三边形中稳定。在给出这一定理的证明后,文中着重指出,此定理并不意味着在任何n+k相多体系的封闭网图或实际相图中都必须存在无对角线的k边形,即使该实际相图具有最大的闭合度。 In this paper, we discuss some properties of the closed network of n + 3 and n + 4 multi-system closed systems. We propose the double-degree combination feature stable polygon theorem of n + k (k≥3) k ≥ 3) A bivariate combination of multi-system, the maximum is stable in a non-diagonal k-polygon of the closed mesh and the smallest can be stabilized in a triangle. After the proof of this theorem is given, it is emphasized in the paper that this theorem does not imply that there must be a non-diagonal k-polygon in the closed or actual phase diagram of any n + k multi-system, even if The actual phase diagram has the greatest degree of closure.