National Science LibraryNSL aims to establish an integrated and digital science information service environment for researchers and students in CAS during 2001-2005. CSDL can be divided into three top-down layers portal, application and resource. resource layer is mainly consist of all kinds of databases such as A&I database,fulltext database, citation database etc. application layer has OpenURL linking server, Cross-Database Meta-search engine,OAI Service providers that can integrated those resource into a universal knowledge platform; portal layer enable user to customizes CSDL information and service and subscribe CSDL via RSS and e-mail??CSDL is based on a library consortia including almost 90 institutional libraries across CAS and tend to incorporate them into a virtual library federation of resource and service. the mission of CSDL Project Coordination Office is to help these libraries to acquire e-resource and establish online service system via public biding.