Guided by the theory of Language Socialization (LS), this study investigates the mediating effects of teacher-student power relations in an academic English course. To do so, several sets of data were collected: responses to a questionnaire survey, a series of semi-structured interviews, and the online interactions which took place on two teaching platforms (WeChat and QQ). Our results show that together with other factors, the power relations highlighted in this study influenced the participants' academic performances. Besides, three types of teacher-student power relations were brought to the fore. Eventually, the power relations identified affected the construction of role identity in our study. The findings provide supporting evidence for the complicated power relations which exist between language learners and their community of practice. [For the complete volume, "CALL and Professionalisation: Short Papers from EUROCALL 2021 (29th, Online, August 26-27, 2021)," see ED616972.]