Abstract This paper applied discussion teaching method to the classroom teaching of physical chemistry, deeply discussed the applicable conditions of total entropy criterion of thermodynamic spontaneous process, and finally summarized important conclusion:the total entropy criterion can only be used to judge the reversibility of the process and not judge the spontaneity of the process directly. In order to further determine the nature of spontaneous process, the total energy exchange between system and environment must be combined with. Through the practice of discussion teaching, students could have a deeper understanding of the applicable conditions of the total entropy criterion of thermodynamic spontaneous process, which could lay a good foundation for the following course study.