Discovery service has as its object to cope with the user to take advantage of the collection of the library as possible to index and search, one step further, the interface by more efficiently to the user's information needs. Discovery service has features such as providing a ranking and navigation services to subdivide the search results by facet results along the suitability and visually rich display, suggestions, recommendations associated resources. In this study introduces the status of discovery services such as discovery service products, usage status, and features, and compares and analyzes the use agencies, content status, main functions, and features of the three discovery services used in Korea library.