On the basis of raster digital elevation model data, flooding range in the Sanxia Region is simulated by using VC 6.0 and ESRI MapObjects. The procedure includes DEM data pre-processing, vector-based and grid-based data integrating, non-source flooding, and source flooding. The results show that flooding ranges can be computed, graphs and images can be visually and dynamically displayed, which means flooding damage may be easily evaluated quantitatively, so as to serve for scientific decision-making in flood management. The case study implemented in the Sanxia Region shows that the model and algorithm are effective.