Mediation theory facilitates teachers and students to tackle the barriers in English teaching and learning process. It offers a sound systematic theoretical fort on which teachers could rely, redefines teachers' roles and functionings in the process of learners' cognitive development and growing self-regulations. The famous psychologist Lev Vygotsky (1978) raised notions in his ZPD theory, Feuerstein (1980) illuminates capable adults as mediators, and defined twelve main features of mediation, which has empirical study value for English teaching. Thus, through quantitative and qualitative research, this paper aims to investigate the perceptions of English teachers' mediation between private university teachers and students, analyze and compare the similarities and differences between them. The results reveal that both teachers and students coming from the two private universities have been aware of the importance of teachers' mediation, however, have different perceptions in the frequency of teachers' mediation. Teachers' actual employment on mediation is weaker than their beliefs on the importance of it.