Based on the tourists' requirements for tourism information, the structure and function of tourism service WebGIS have been systematically designed with Silverlight technology. According to the requirement of systemic construction, the key technologies have been studied and analyzed, including Silverlight, WebGIS, and database technology. Finally, the tourism service WebGIS in Kaifeng city is developed using Silverlight. The results show this platform satisfies tourist's various requirements, such as path analysis, query, multimedia display and assistant decision-making.