The doctrine of Won-Buddhism(Wonbulgyo) is based on the Il-Won-Sang(One Circle) as well as the Fourfold Grace. The teaching of Fourfold Grace is the more distinctive and practical doctrine. Jung bin Park (1891-1943), the founder of Won-Buddhism, originated Won-Buddhism after "the great enlightenment" in 1916. He re-created it from Korean traditional religions. The doctrine of fourfold Grace emphasizes following things: the grace of heaven and earth, the grace of parents, the grace of neighbors, the grace of law. The doctrinal chart of Won-Buddhism shows the relationship between the truth of Il-Won-Sang and the fourfold grace as the whole to the part, and unites the faith and gratitude to be practiced whenever and everywhere. Two different grace theories from Sotaesan and Apostle Paul, are compared through out this article. First, Sotaesan understands god as pantheism but Apostle Paul, as creator. Second, salvation is gained from one’s good deeds according to Sotaesan but Apostle Paul asserts that salvation is gained only by the blood of Jesus Christ. Last, while Soetaesan emphasize religion of ethic, Apostle Paul emphasizes religion of life. I strongly suggest three mission strategies to believers in order to evangelize them. First, Christians have to witness the uniqueness of Jesus Christ to Won-Buddhism who believes in syncretism. Next, Christians have to change their Won-Buddhism world-view into Christian world view. Finally, we have to persuade them through love and patience.