“Kuai······le” is one of the common structures in spoken Chinese. “Kuai” is an adverb of time, which means that something is close to or about to happen soon. “Le” is auxiliary word, which means change. The words or phrases which can be put into “kuai······le” can be a noun (phrase), or a verb (phrase), or an adjective (phrase), or a subject-predicate phrase. However, not all nouns, verbs, adjectives and subject-predicate phrases can be put into this structure. This article discusses the words or phrases and their meanings which can be put into this structure, which words or phrases can put into this structure and which can not, and also explains the reasons why they can or can not be put into this structure.