Social networks have been investigated as an important factor to understand social and language innovations for decades. Most researchers focus on one-language-dominated societies when studying social networks' influence on language practice while studies on bilingual societies remain scarce. In this study, we examine how Chinese graduate students in Catalonia with L2 Spanish acquire Catalan in their social networks. In-depth interviews have been carried out individually with 23 participants and conversation recordings were collected. The data were processed using qualitative approach and conversation analysis. Participants' interactions with Catalan NSs can be categorised into 3 groups: active engagement (communicating mostly in Catalan), semi-active engagement (Spanish and Catalan translanguaging), and passive engagement (listening to others talking in Catalan without intervention). The Catalan NSs in their social networks help them with their Catalan learning in 3 aspects: 1) providing useful information; 2) giving instant feedback and corrections; 3) acting as authentic and idiomatic oral expression example. Participants are also aware of the drawbacks of learning a target language in a bilingual society, that the interactive opportunities may decrease due to the common use of Spanish and some NSs may speak a mixture of Spanish and Catalan, which has negative impacts on their Catalan acquisition.