According to the spatiotemporal distribution characteristics of the rainfall and the geographic features, China is divided into four rainfall areas. On this basis, we developed the different assessment methods of the intensity grade of the heavy rains for every rainfall area. At the same time, elevation, standard deviation of elevation, drainage density and soil types have been identified as import controlling factors of the torrential rain disasters, and these factors were respectively classified into different grades. The comprehensive rainstorm disaster risk assessment model is established by weighted summation of the rainfall factors and the selected controlling factors. Based on the model, we further applied GIS to evaulate the number of affected urban and rural residents and land areas in different risk levels. Compared with the previous rainstorm risk assessment models, this rainstorm risk assessment model can be applied more widely in any regional rainstorm disaster risk assessment. Moreover, this model has stronger operation ability of pre assessment, realtime assesment and postassessment by using realtime or forecast rainfall data. Finally, combined with GIS, this model can achieve quantitative evaluation of the hazardaffected bodies at the different risk levels.