Abstract: With frequent natural disaster occurrences and extreme climate change, the research on comprehensive risk assessment of storm disaster is significant. Based on GIS technology, the authors statistically analyzed the risk of rainstorm & flood disaster in Deyang, and made a quantitative research. The AHP method and Delphi method were combined to establish a system of rainstorm and flood disaster risk assessment in Deyang. The system included 4 indexes, hazard of disaster inducing factors, exposing of hazard affected bodies, sensitivity of hazard inducing environment and capability of disaster prevention, in order to ensure the rationality. According to the results, Deyang could be classified into five levels of risk regions: negligible risk, low risk, medium risk, high risk and very high risk. The authors discussed the prevention of rainstorm disaster in high risk and very high risk regions, and provided countermeasures to reduce the probability of loss and casualty.