Based on the development of the traditional power business expanding system， this paper combines the MIS（management information system） and GIS（geographical information system） by employing an object-oriented analyzing method and plug-in models. In this way， the GIS gives great spatial data support to the MIS. The design and implementation of a spatial assistant decision support system for expanding power business are proposed. A cooperative system is built by adopting large system cybernetics. The database is divided into the power synthesis database， the method database， the model database and the knowledge database supported by Oracle Spatial. The system can be implemented with flexible workflow scheming and workflow real-time tracking， and model database and its management system are introduced into the GIS while offering automatic optimum solution based on the combination of the decision tree， improved Dijkstra and A*algorithms. In addition， it is also pointed out that the key technologies such as the association of spatial and attribute data etc. are of academic significance and have broad application prospects.