In political theology, both Reinhold Niebuhr and Paul Tillich belong to liberalism, but they hold very different views on the agent of political activities, the ontological ground of human being and the essential questions in real political field. The keypoints are: ( 1) On the agents of political activities, Niebuhr emphasizes the sinfulness of individual and Tillich emphasizes the image of God in human being. Niebuhr holds that groups as the agents of political activities have their own personhood, but Tillich denies it. (2) In history, Niebuhr thinks that it consists of dramas because of God' s will and Tillich thinks it takes places in an ontological construction and therefore has its own law. Niebuhr emphasizes the Trinitarian construction of human being's freedom and Tillich emphasizes the Trinitarian construction of the Being itself. Niebuhr denies the Natural Law, but Tillich emphasizes it. (3) To the political authority of real political life, on the relationship between the ruler and the ruled, Tillich appeals to the central point of political power and Niebuhr appeals to the balance of political powers. On the consent of the ruled, Tillich considers its legitimacy based on the logical relationship between the center and the boundaries from the point of the order of the community, and Niebuhr considers its legitimacy based on the actual relationship of tradition and real life from the sublimity and the hierarchical order of the community. On the acquiesce of the ruled, both Tillich and Niebuhr emphasize acknowledgement. However, in Tillich's thought, its essential ground is the spirit of the community and its center is the mystery experience from Eros and Sophia; in Niebuhr's thought, its essential ground is the justice of administer and its center is the moral authority.