This paper draws on the recently theorised notions of space and scale in sociolinguistics to investigate the complexity and micro-variation of the Chinese language in the context of mass internal migration, and the way in which sociolinguistic processes shed light on the construction of migrant identities. In spite of the enormously rich diversity in Chinese languages, images of linguistic stability and homogeneity overlie the societal diversity that characterises every real social environment. The monoglot ideologies focused on Putonghua often present obstacles for migrant workers whose Putonghua proficiency is limited, and disqualify their existing language resources and skills. Three vignettes will illustrate this. The first one demonstrates the presence and influence of Putonghua in an eastern coastal city through a story told by a migrant child; the second vignette reveals how a migrant worker's regional accent is misrecognised in the interactions with the locals; and the third vignette illustrates how a migrant worker is polyglot in one language and how this polyglot repertoire is organised indexically in relation to layered and stratified spaces. Therefore the monoglot ideologies often disqualify some people's linguistic resources; many migrant workers nevertheless develop a polyglot repertoire and navigate such obstacles.