Abstract: Two-port linear network is an important content of circuit foundation as a university course. The textbook questions related to the two-port network are generally solved by reciprocity theorem, and sometimes the superposition theorem is also used. In response to the difficulty in teaching resulted from abstract reciprocity theorem, and based on the actual teaching experience and equivalent analysis, the article proposes the concept of equivalent circuit and designs the equivalent circuit inside the two-port network, in a bid to simplify the question and the teaching for students, which also offers some guidance to the teaching of two-port linear network.