With the deepening of the new curriculum reform, the cultivation of Key Competencies has become a key task in subject teaching. The Key Competencies of the mathematics discipline reflects the nurturing value of the mathematics discipline and has an important role and significance for the growth and development of students. The classroom is the main position for cultivating students' Key Competencies and imparting knowledge, so it is very necessary to improve the efficiency of classroom teaching and cultivate students' Key Competencies. This paper analyses the importance of improving the efficiency of classroom teaching in the context of Key Competencies and the current status quo of junior middle school mathematics classroom teaching, and on this basis proposes strategies to improve the efficiency of classroom teaching, to promote the cultivation and enhancement of students' Key Competencies.