The general way to technically implement the GIS data sharing in early days was the adoption of geographic encoding based on some classifications. The reason for this is the perception that the codes used to represent the geography is unique. But the practices in recent years have proved that the method above is of little use in data sharing. This article has given a GIS Semantic Data Model to try to solve the problem of data sharing. A theoretical frame as well as the strict definition of related concepts have been given in this paper. An application related to the design of NREDIS has been introduced to verify the applicability of the proposed model. Some further work has been listed in the last paragraph.