Vi+NP is an intransitive verb followed by a noun or noun phrase. Over the years, there have been many scholars undertaking study of this problem and put forward different views, but they have not yet reached a satisfactory explanation. This paper explores decategorization theory on the structure of Vi+NP, and analyzes the syntax of Vi and NP in Vi+NP structure, separately from the four perspectives of Vi+NP pragmatic characteristics. Moreover, it comes to the conclusion that the variability of linguistic rules and the psychological cognitive motivation are the most essential mechanism and internal motivation for decategorization features of Vi+NP structure, which tries to clarify the pragmatic construction and interpretation of Vi+NP structure.