This study investigated why object-gap relative clauses (RCs) are dominant in early child Mandarin. We discuss how restrictive-RCs differ from pseudo-RCs syntactically and pragmatically, and examine how these two types of RCs are distributed in the RC utterances of ten children and their caregivers. The results showed that (a) Mandarin-speaking children produce many more pseudo-RCs than restrictive-RCs, (b) restrictive-RCs exhibit a subject-gap advantage and are dominantly headed, and (c) pseudo-RCs exhibit an object-gap advantage and are dominantly headless. We propose that the development of restrictive-RCs is mainly influenced by the structural factor, and that the extensive use of pseudo-RCs is attributed to the communicative needs of young children. Our findings also suggest that young children's pseudo-RCs tend to have a subject-focus reading, and the object-gap dominance observed in the pseudo-RCs of child Mandarin is related to the head-final RCs and the special structural features of the cleft construction in Mandarin.