In order to promote the professional development of mathematics teachers in primary and secondary schools in China, many schools have put forward the task of observing Classroom teaching. Theoretically, this is definitely a valuable activity. However, in practice, many teachers responded that they did not feel much gain from it and did not like it. What is the reason? It is undoubtedly meaningful to probe into the factors, find out the deficiencies, and make reasonable corrections based on the current reality.