Abstract: Case based reasoning(CBR) is an effective method to solve DFA and Assembly Planning problems, while assemblies retrieval and indexing is a primary step to its application. In this paper, the connection relations of assemblies are formally expressed and categorized, and then quantitative method for comparing two connection relations is proposed. Based on bipartite graph theory, similarity calculation model of assemblies is constructed. Assemblies retrieving process is described and a computation example is presented.