Legal deposit system is an important legal instrument for national libraries. But the law or act based on print materials in many countries predates the current information age and requires a new legal framework in order to encompass electronic publications. Many national libraries, therefore, are seeking to encourage their governments to establish legal deposit for publications in the whole range of formats. The purpose of this paper is to analyse a world-wide trends of the legal deposit system for on-line publications as well as off-line materials. The result of this analysis will be used to develop a new model of legal deposit system in Korea.