national science library(nsl) 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 ai database,fulltext database, citation database etc. application layer has openurl linking server, cross-database -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.