The use of Chat GPT in the classroom has been receiving widespread attention, but research on its impact on the role transformation of middle school teachers is still lacking. This paper analyses the challenges that the application of Chat GPT poses to teachers and classroom teaching in Chinese public junior high schools. The analysis concludes that the application of Chat GPT will challenge the teacher's subject position as a single lecturer, the traditional knowledge system, and the classroom teaching model. Students' information literacy will also affect the consequences of the use of Chat GPT in the classroom. Based on these findings, this paper proposes the following suggestions: teachers should be transformed from traditional single-classroom instructors, skilled laborers, and professional knowledge transmitters into leaders of human-computer collaborative teaching, explorers of innovative classrooms, and leaders of information literacy. In this way, teachers in public junior high schools could find themselves still important to students in the classroom.