The purpose of this study is to know the trends of research of reference service in Korea before 21th century from beginning. After analyzing of representative subject bibliographies , domestic research of this field can be devided into four chronical stages; the beginning stage in 1950’s, the changing stage in 1970’s, the developing stage in 1980’s and professional stage in 1990’s. And found out both domestic and internaional research seemed to have focused on the service theory, however there have been some differences in their lower subjects.