The web service is a main working pattern and a significant application model for next generation Internet application. The service-oriented architecture is a very promising architecture for practical implementation of the next generation geographical information systems. This paper investigated the service-oriented architecture for constructing a distributed and web service enabled geographical information platform. The GIS platform architecture is designed as a multi-layer architecture that integrates the web service, Servlet/JSP functions and GIS APIs based on the framework of J2EE infrastructure. The web service framework was applied to the GIS system design and implementation. GIS web services were designed to provide the hosted spatial data and GIS functionality to integrate the customized GIS applications to perform basic geo-processing tasks, such as address matching, map image display, and routing, without maintaining GIS tools or the associated geographical data. The system architecture, functions, system integrations, and some key technical problems were investigated. It has an important application prospect in the GIS tools development and application.