For the advance of the Korean Society into post-modern, Wonbuddhism, which has experienced both the beginning and development of Korea's modernization, should have to grope its own change according to the new age. Wonbuddhism's opening motto "as material civilization develops, cultivate spiritual civilization accordingly" includes the meaning that the spiritual grand opening, Wonbuddhism has sought, is to realize the true moral world with the harmony of both spiritual and material cultivation through the appearance of new human spirituality. But, the interpretation on it had depended mainly on modern logics or on corresponding logics on westernized cultivation. This explanation had provided the proper axis of ideology and spirituality in the process of the Korean industrialization and played the main role on the Wonbuddhism's development from the 1970s to the 1980s. However, although Wonbuddhism had the background of its beginning in the Korean modern society, the main point which Sotaesan and Wonbuddhism oriented is not only on the modern industrial society. This study is to find the identity of Wonbuddhism in post-modern society through the reinterpretation on Wonbuddhism's theory of Great Opening in Mind. Conclusionally, Wonbuddhism's theory of Great Opening in Mind has the monistic meaning of material and spirituality, not the dualistic meaning. And its methodology and development has the significant difference with the theory of Dongdoseogi at that time. Through Wonbuddhism's theory of Great Opening in Mind, we can find both the directions of social reform on the world at large and the methodology of personal spiritual discipline. Moreover, we can understand that it represents the practical theory and direction of our usual life which can be explained as Samdongeully. Under the title of post-modern society and Wonbuddhism, the reinterpretation on Wonbuddhism's theory of Great Opening in Mind can be an important issue to reconfirm Wonbuddhism's identity and to suggest the new direction of Wonbuddhism in the new age.