Through extensive interviews with Hui, Han, Dongxiang, and Tibetan migrants and participant observation in northwest China between 2013 and 2015, we examine how the negotiation of ethnic identity influences acculturation strategies in three cultural contexts by scrutinizing the three operational aspects of ethnic identity: perceptions, affections, and behaviors. We argue that the ethnic identity is negotiated at both the group and individual levels as a relation of dialectical unification in regard to fixity and fluidity. At the group level, ethnic identity is relatively fixed and rigid and is perceived by most of the group members as the social norms which normalize ethnic behavior collectively. At the individual level, on the other hand, ethnic identity can be highly flowing and contested from one individual to another. Han identity is generally self-perceived as unmarked, porous, situated, and sometimes even vacuous. Han migrants' acculturation is more dependent on the cultural context of the host society. Hui and Dongxiang migrants show a strong attachment and affective bonds to their ethnic identity, which is largely based on religious identity. Although Tibetan migrants perceive a complex, place-based identity related to their religion, the grassland, their traditional ways of living, and their language, a Tibetan identity seems to be difficult to fulfill given their economic vulnerability and the contradictions between retaining traditions and being Sinicized in the city.