Abstract: The paper studies modern mandarin Chinese prepositional groups from the perspective of the Cardiff Grammar, discussing the components of the prepositional group and the elements it can fill.The paper also focuses on the semantic and the syntactic analysis of some special clauses such as "preposition-X-postposition", "ba" constructions, and "bei" constructions.The paper aims to provide a new perspective to analyze the syntactic structure and functions of modern mandarin Chinese prepositional groups.It finds that Chinese prepositional groups contain prepositions and completives, and it can fill Subject, Complement and Adjunct at the level of clause, and Modifier and Finisher at the level of group.