The paper introduces characteristics of the mobile client and its application and services in foreign libraries and analyzes the possibility to apply the APP in medical libraries in China. It emphasizes measures for publicity, promotion and popularization, including deepening the understanding, expanding the service scope, cultivating the habit of use, analyzing big data of users' information behavior, excavating potential demands, developing network payment, GPS positioning, promoting electronic information borrowing, developing library APP, training technicians of library APP, etc.