The quality of classroom teaching is the most direct and critical factor of the level of school education and teaching，which is related to the learning effect of students and their performance after graduation. Teaching diagnosis and improvement is a new discourse system in recent years. It is an important measure to ensure the quality of education and teaching, involving schools, teachers, students and courses, etc. The diagnosis and improvement of classroom teaching quality is a new exploration for higher vocational colleges. This article explores the diagnosis and improvement path of classroom teaching from the following aspects: the establishment of modern quality culture, the establishment of diagnosis and improvement mechanism, and the reform of teaching evaluation. Exploring the path of classroom teaching diagnosis and improvement provides new ideas for accurately diagnosing the problems existing in classroom teaching, continuously improving classroom teaching, promoting teaching reform and improving classroom teaching quality.