Abstract:Flood risk can, in general terms, be defined as probability time conse quence. It consists of flood hazard analysis, vulnerability analysis and damage evaluation. At present, there are many studies on the flood disaster risk assess ment, which is mainly by constructing evaluation system or regional torrent risk zonation based on GIS, but few researches are by using the combination. The GIS has been chosen to quantitatively represent the influencing fact ors, spatialize the data into the uniform grid system, and transfer all the data items into the effect degrees on the probability of flooding, and based on cons tructing evaluation system and combining GIS, the flood risk assessment and regi onal torrent risk zonation are analyzed. Finally, a categorical model for flood risk zonation has been put forward. The approach has been applied to the Henan P rovince flood disaster risk zonation. The accuracy of evaluation system by givin g weight and the significance of regionalization map are provided. The case stud y shows that the GIS based category model is effective in flood risk zonation. Therefore the paper has a certain theoretical and practical significance. The re sults of zonation show that the possibility of flood disaster risk is the bigges t in the three urban districts of Xinyang, Zhumadian and Zhoukou because the ind exes of rainfall on flooding and vulnerability of socio economic properties are relatively high. Because of the higher influence indexes of river density in Ji aozuo, Kaifeng, Zhengzhou, Anyang and Puyang in the reaches of the Yellow River, the flood disaster risk in these areas is higher. However occurrence of floods in other areas is very few.