Abstract: Though GIS industry in China has made an unprecedented progress in recent years, there exist difficulties and challenges due to all kinds of reasons such as the lack of proper policies, standards for data sharing, high-quality technical personnel and so on. Obviously, it is very important for most of GIS users to get geospatial information quickly and easily. The development of Interent and corresponding techniques makes it possible. National Geospatial Data Clearinghouse (NGDC) is a distributed network of geospatial data producers, managers, and users linked electronically (Clinton, 1994). It is one of the most important activities in the National Spatial Data Infrastructure (NSDI). What's more, it will be in favor of the nation-wide geospatial data sharing and decrease the repeated investment of the GIS industry. Based on the authors' experiences of setting up a NGDC model Web site, this paper attempts to present some significant aspects about the security of NGDC based on active server puges (ASP). They include data storing, database maintenance, new technical supporting and so on. Firstly, this paper analyzes how to provide the security of data which is saved in the hosts of NGDC. The security model of "Networks-DB Server-DB-DB Object" is also presented in it. In Windows NT Server, Internet Information Server (IIS) is in charge of transferring message and the management of Web sites. ASP is also based on IIS. The advantages of virtual directory technique provided by IIS are emphasized. As a NGDC Web site example, the NGDC model Web site at the Research Center of GIS in WTUSM is also mentioned. Because it is only a model Web site where the transmission of digital spatial products is not included in the functions. However, the management of spatial metadata is more important and some functions of metadata query are implemented. It is illustrated clearly in the functional diagram of the NGDC model Web site.