Abstract: The author has developed a data model named the Basic Kinematic Chain (BKC) code set, which is applicable for kinematic structure of mechanisms and its coding principle. He has proposed that every BKC is coded by an integer of 5 decimal digits and composed of the labels of two ends and the number of binary vertices of the BKC. In this paper, a method to detect isomorphism by comparing two BKC code sets with each other is presented. Through this method, the two mechanisms are isomorphic if their BKC code sets are matched. The BKC code set is equivalent to the adjacent matrix for a topological graph, and its uniqueness is ensured, however, it saves much time to perform the calculations.