Case-based reasoning system takes a symbolic path to model legal artificial intelligence,use logic to portray the process of case-based reasoning.However,traditional logic tools are difficult to portray and express the defeasible process in the case-based reasoning process.The logical model of the case-based reasoning system can be reconstructed,and the intelligent boundaries of the case-based reasoning system can be clarified,as using the tools of argumentation schemes in argumentation theory to parse the working principle of the classical case-based reasoning system Hypo.The reflection on the similar-case systems in the current judicial practice,which is based on the analysis of the logical model of the case-based reasoning system,can prove the basic principle of artificial intelligence-assisted justice.