This study has been aimed to analyze the following three points which are believed to be the most important in establishing efficient library networks. The writers have done the research into the literature and references concerning the networks of library, as they are considered crucial functions in cooperative administration between the libraries. The following are the findings from the survey: 1) The established networks in foreign countries have been compared with those of Korea, basing upon the data and present situations in both areas and the definition and agreed viewpoint of the networks are presented. 2) The relations between the existing Library system and Consortia were clarified in view of the current trend, thus showing the scope and integral aspects of them. 3) Finally, we have classified the types of network into four categories, such as search service network, customized service network, service center/network and state local networks, and made through analysis of the character, organization and management of each realm.