Poyang Lake wetland, one of the world's six major wetlands, was taken as the research object. The theories and technologies of geographic information system, remote sensing, global positioning system, spatial database, three-dimensional virtual simulation and hydrodynamic theories were adopted to construct the fundamental geographic information system for Poyang Lake wetland, which integrates the expert knowledge, model and decision making functions. To a certain extent, this system solved the contradictions in wetland economic development, in which different sectors (e.g. environment, water conservation and land planning) are closely related, but are at the same time isolated from each other. And to some extent, this system realized systems integration development, three-dimensional modeling and simulation for hydraulic engineering, and the dynamic simulation and forecasting of flooding based on 3D WebGIS.