This article examines the grammaticalization of Bian 便 from ancient Chinese to early Mandarin Chinese by tracing its evolvement of using as a verb into twelve syntactic functions and accordingly constructs its path of grammaticalization. In the path the consecutive and emphatic adverbs are two key grammatical functions since most adverbial and conjunctional functions of Bian are derived from them. In addition to Bian, Ji即 and Jiu 就 underwent the same path of grammaticalization and also have developed the twelve functions as Bian has. This similarity indicates that the path of grammaticalization we propose in this article is representative in the history of Chinese language. My article also discusses the syntactic and semantic properties of consecutive and emphatic adverbs in order to explore the cause of Bian’s polygrammaticalization and thus confirms that the development of the three words does not contradict the hypothesis of unidirectionality.