This study studies theological realism of Reinhold Niebuhr. This study provides an opportunity to think more broadly about the traditional ‘realist ethics’ used in Christian political theology. The Korean meaning of ‘realism’ or ‘reality’ can be interpreted in a variety of ways like ‘exist,’ ‘realism,’ ‘fact,’ ‘straightforward,’ ‘status,’ ‘situation,’ ‘temporary,’ ‘phenomenon,’ ‘misery’ and even ‘reality of the kingdom of God,’ which is given in grace beyond all conditions of reality. From this point of view, Niebuhr’s theological realism opens the horizon for human existentialism, which allows us to interpret the present problems in the world in greater depth. This paper holds the meaning of the word ‘reality,’ expanding the horizon of meaning to suit the context of the context. Therefore, this paper presents a way for the concept of ‘theological realism’ or ‘reality’ understood by Niebuhr to go beyond the problem of political reality, to help build the theory of responsible self through the theory of existence associated with God, and, above all, public theology in this post-Corna19 era.