This article clarifies the process by which missionaries resolve through debate and debate on the problem of the polygamist, which was one of the challenges faced by Korean missionaries in the early days as Christianity was accepted in Korea during the transition period. Christian family ethics, or marriage. Its pur- pose is to track the process by which ethics is being implanted and established. Traditionally, in Korean society, monogamy system existed in form, and con- striction was openly allowed. In the light of Christian doctrine, the custom of constriction could not be allowed, but the issue of dealing with polygamist also revealed differences in theology among missionaries. In 1895, the Methodist Church organized that polygamist, regardless of gender, could not enter or enroll in the Methodist Church. The Presbyterian Church began in 1894, and in 1897, it was established at the annual meeting of the Korean Mission, attended by Speer of the North Korean Presbyterian Mission. It should be noted here that W. L. Swallen is a moderate position on the self-serving of a member of the church of , and insists on the principle of principle. At the annual meeting in 1897, the position of William M. Baird who insisted on principle rather than the moderate theo- ry of W. L. Swallen was accepted. This stance that a big man cannot become a member of the Church persists after that. The debate on the serious marriage between Swallen and Baird is the basis of the marriage ethics of Christianity in Korea, and it can be evaluated that Korean society has played a certain role in the transition from formal monogamy to practical monogamy.