By referring to the theory of Park, this article attempts to understand the truth in Journalism with a new perspective. The research suggests that truth in journalism is not about truth itself but assumed truth. As a form of knowledge, news report has to establish its legitimacy in two ways. For one thing, news report must be accepted by audience. For another, the media must realize the legalization of themselves. As for the former, assumed truth from audience challenges the legitimacy of news report constantly. As for the latter, the media has to pursue the truth consistently in order to attain legalization. On this basis, truth in journalism has become a professional standard of the media at the same time. It can not only help the media to be recognized by others, but also become a discourse strategy of the media to resist others.