Abstract: Postmodernism is an extremely ambiguous cultural phenomenon, which is "uncertain". Its uniqueness lies in the following aspects:the postmodern cultural mentality which is unpredictable and difficult to express, the thinking mode of combing creation with life, the thoughtless postmodern thinking mode, the postmodern thinking mode which has nothing to do with "truth". The cultural mentality and thinking mode should be criticized and negated correctly. And it should be recognized that "uncertainty" gives more space for thought and weakens the stability of the whole social thought.