研究了一类n 阶三脚架网络的等效电阻模型，该模型含有7 个不同的电阻元素，因而包含了多个网络模型. 文章采用构建等效模型的方法导出了一个非线性差分方程模型，采用变量代换的方法间接地给出了非线性差分方程的通解. 本文进一步创造了一个负电阻的概念，获得了电阻网络任意节点间的等效电阻公式. 利用特殊条件下的数个特殊例子与相关结果进行了比较. 本文的结论也适用于复阻抗网络的等效复阻抗研究.

We study the equivalent resistance of an n - step network with tripod structure，which is a profound problem，has not been resolved before. The network model contains seven arbitrary parameters which make the network contain a number of different types. First of all，we establish a nonlinear difference equation by means of simplifying a complex graphics into a simple equivalent model; next，we construct the method of equivalent transformation to obtain the general solution of the nonlinear difference equation. Finally，we create a new concept of negative resistance for the needs of the equivalent conversion，and obtain two general resistance formulae of an n - step network with tripod structure. We compare several results by making use of a number of specific examples in 　　the special conditions. Our method and the results are suitable for the research of complex impedance network as well.