Fandom has become a social and cultural phenomenon reflecting practical activities in the fan community. The prevalence of social media and online fan communities has facilitated the transnational industries of Korean popular culture (K-pop) in mainland China. Fans are enthusiastic about creating posts dedicated to their idol(s) or music bands to broaden the influence of the celebrities and establish personal connections with them. The unique interaction patterns in the K-pop fan community reflect the process of fans’ identity identification and construction. This article explores how mainland fans employ discursive strategies to construct their identity and legitimize their behaviors on social media. A total of 80 posts in (G)I-DLE Super Topic made by mainland China netizens have been collected from Sina Weibo. The findings illustrate the construction of both individual and collective identities among fans, which are shaped by various contexts and different communicative purposes. Further analysis explores the potential impact of fans' identities within online communities on the K-pop market in mainland China.