As the global climate change and accelerating the process of urbanization, flood disaster becomes increasingly serious. Based on risk identification, evaluation index is selected from hazard factors, disaster environment, hazard bearing body and disaster prevention and mitigation. Evaluation index system is established. Using the analytic hierarchy process (AHP) to determine the criteria weights, Based on ordered weighted average (OWA) to calculate the order weights. Build OWA-GIS flood risk assessment model to evaluate flood risk in Chaohu Basin. The results show that the high risk is in southeast of Chaohu Basin, especially Lujiang, Wuwei, Juchao district and He county. Low risk areas are mainly distributed in the southwest, northwest and north of Chaohu basin, especially in Shucheng, Feixi and Feidong county. With the increase of the decision coefficient, the decision maker's attitude from optimism to pessimism, risk is also growing. The flood risk assessment based on OWA-GIS is a scenario analysis, evaluating risk status under different decision attitudes. More complex scenarios can be developed to predict the risk under certain natural and economic conditions and different decision attitudes in the future. The study provided scientific basis for planning and disaster risk management.