At present,China's graduate education has developed rapidly and the enrollment scale has been expanding continuously, but at the same time, there are many problems in graduate education, and alienation of teacher-student relationship is one of the typical problems. From the perspective of Simmel's "boundary theory", this paper finds that the "ambiguous boundary between power and responsibility, interests and actions" is an important reason for the alienation of the teacher-student relationship. Therefore, it is the key to prevent and dissolve the alienation of teacher-student relationship by perfecting the system norms of teacher-student relationship, advocating the concept of equal interaction between teachers and students, and then constructing a clear boundary.