Some learners and instructors of English language are inclined to consider the phrases like"you know""well"to be meaningless pause-fillers, which only exist to make the utterance fluent, thus they don't like to use them too often in speech. This article gives a psycholinguistic study of the discourse marker"you know", not only does it relate the use to the speaker's complex cognitive process in the production of speech, but also it illustrates how"you know"functions in the interaction between the speaker and the hearer. Finally, we come to conclude that it is useful and meaningful in our speech.