Abstract:Most prepositions evolve from verbs. However, previous researches have rarely indicated that the Chinese "Yue" has been prepositionalized, though it shares the same structure as the Chinese "Zai" which is considered as a preposition. This has caused a conflict in analyzing the same grammatical structure. To fix this problem, this paper investigates into the word "(Da)Yue" diachronically and synchronically based on the Chinese Corpus from the perspectives of the changing relationship between the subject and the object, the diachronic change of the sentential length, and the grammaticalization process of prepositions. The investigation shows that "Yue" is not necessarily the abbreviation of "Da Yue", and that "Yue" has experienced a process of grammaticalization. This process includes a semantic objectification, a morphological boundarization, and a structural subordination and degradation. To conclude, the Chinese verb "Yue" tends to be prepositionalized and now has been unified as both a preposition and an adverb. This research has testified an applicable and simple mechanism for grammaticalization, prepositionalization and so on.