This research compares and analyzes the legal deposit of national online electronic publishing and related laws that were recently amended in order to preserve the exponentially increasing number of electronic books(e-books). Based on the analysis, it also seeks ways to initiate a legal deposit system of e-books in South Korea. The research, therefore, defines the exact range and types of e-books. This research proposes three conditions to introduce the legal deposit system in order to preserve South Korean e-books. The first is to establish a clear definition and classification of e-books as data subject to legal deposit for preservation purposes. The second condition is to establish a legal system in order to deposit and collect network(online-exclusive) type e-books. The final condition is to reflect the opinion of publishers and to create security measures against any loss of the companies.