Southeast China coastal areas belong to subtropical monsoon climatic zone, thus easily affected by floodsresulted from typhoons and rainstorms. Since the areas of river basins are smnall, rivers flood regulation capacities arelow, and therefore flood hazard is grave. In this paper, taking the Yongjiang basin in southeast China as an example, theapproaches and methods of geographic information system(GIS) applied to flood disaster control and reduction researchon small basin are explored. On GIS help the rainfall-runoff calculation model and the river channel flood routing modelare developed. And the evaluating flood submerged area and the damage assessment models are built supported by digitelevation models. Lastly the decision support system on GIS supported for flood control in research basin has been set up.This greatly improves flood-proofing decision-making capacities in river basin, and provides valuable information and amode for flood prevention and reduction in the medium and small basin. Meanwhile, the research indicates that technolo-gies of GIS provide a powerful tool for flood disaster control.