Kan "看" is a complementizer that can lead a clause. It can be located in a sentence or at the end of a sentence. It is located at the end of a sentence because the clause it leads has no phonetic realization due to oral omission, but in the process of meaning interpretation, potential subsequent sentences can be added. This omission causes Kan to look like a tentative auxiliary on the surface, but it is still a complementizer. This difference is related to the stylistic environment used in the grammaticalization process of Kan, which gradually occurs in the process of oral use, and thus has the characteristic of ellipsis in the use of oral language. According to the different syntactic positions of Kan, the paper will try to find out the common features in the use of kan in different positions, and further demonstrate the usage of Kan as a complementizer.