本文试图论证两则四端网络定理.定理一为“纯电抗四端网络的最大可得功率增益G或为1;或为0.当网络确能传输功率时,G=1;当网络根本不能传输功率时,即输出端与输入端无耦合时,G=0”.定理二为“对于确能传输功率的纯电抗四端网络,当其输出阻抗与负载达到共轭匹配时,输入阻抗亦必与信号源内阻抗达到共轭匹配;反之亦然.”应用这两定理的概念,在处理若干问题时,较为方便. This paper attempts to demonstrate two four-terminal network theorem. Theorem one is “pure reactance four-terminal network maximum available power gain G or 1 or 0. When the network can indeed transmit power, G = 1; when the network simply can not G = 0 ”when the power is transmitted, that is, the output is not coupled with the input. Theorem 2 is“ For a purely reactive four-terminal network that can indeed transmit power, when its output impedance matches the load, the input impedance The impedances inside the signal source must be conjugate-matched and vice versa. ”The concept of applying these two theorems is more convenient when dealing with a few problems.