Digital library is a library that uses digital technology to process and store all kinds of graphic documents, which is essentially a distributed information system for multimedia production. It uses digital technology to store various information resources in different carriers and different geographical locations, so as to facilitate cross-regional and object-oriented network query and dissemination. It involves the whole process of information resources processing, storage, retrieval, transmission and utilization. Generally speaking, the digital library is a virtual library without walls, an extensible knowledge network system based on network environment, a super-large-scale, distributed and easy-to-use knowledge center, which can realize seamless linking and intelligent retrieval across databases and is not limited by time and space.