To improve the risk management of flood disasters, risk assessment of flood disasters of 1983 and 2010 in Ankang City was conducted using the cloud model. Eight typical indexes were selected to establish an assessment index system based on field investigation. The entropy method was used to calculate the index weights, and the cloud model was introduced to obtain the membership degrees of flood risk. Through conversion between the index weights and membership degrees, the levels of flood risk of 2010 and 1983 were obtained by means of the principle of maximum membership. Results show that the level of flood risk of 2010 increased as compared to that of 1983 in Ankang City, but the risk changes were different in some counties. Areas with high flood risk were mainly concentrated in the Hanbin District and Hanyin County, and the sizes of those areas were almost unchanged. Areas with relatively high or low flood risk increased, while, areas with moderate or low flood risk decreased. The conversion between adjacent levels of flood risk is the natural behavior when the flood risk increases.