Although university libraries run by the subject-oriented serviec systems are increasing more and more, many problems are emerging as a result of tying out the subject classification of the sources without an enough advance knowledge, consideration of reality, and the study about effective management of subject-oriented sum system. Through the research of 37 university libraries run by the system of subject-oriented service, it was proved that for the effective subject-oriented service system, the reasonable classification of the subjects, considering the form and structure of the building, the number of users on each subject and the organization of the collection, and the subject librarians, who would take charge of subject-oriented service systems are indispensable. Therefore, the subject-oriented service system to be rooted strongly, the role model of the subject-oriented service system adequate to the reality of Korean university libraries should be developed, and the efforts of the people on the spot such as acquiring enough supports and training of the subject librarians should be arranged.