Human activities result in environmental problems at a very fast speed, especially polluting the natural resources. It’s imperative to protect the lake effectively. Geographical Information System proves itself an effective way under such complex conditions. MapObjects, a powerful geo-related component has been wildly applied in the related area. This paper discusses the characteristics and functions of a lake pollutant geographical information system, discussing the regular process of constructing the system. Result shows that establishment of data structure and spatial database is one of the most important parts of constructing a MapObjects supported geographical information system.