This paper argues that the clausal structure of Mandarin Chinese contains an object clitic projection (SuoP). The discussion is based on the syntactic behavior of the particlesuo, which occurs when syntactic movement of an accusative NP has occurred.Suo is triggered when the movement has proceeded through SpecSuoP. Drawing the evidence fromsuo, I argue that Chinese inflectional structure contains Case projections: NomP (nominative Case projection) and SuoP (accusative Case projection). The presence of these projections has far-reaching consequences for the analyses of various syntactic constructions, such as relative clauses, thebei-construction, and topicalization structures. An unified analysis is given to these constructions.