Based on the environmental Gini coefficient, this study investigated the allocation of regional flood drainage rights in the Sunan Canal. The population, GDP, and land area of urban flood control regions along the canal are selected as the control indexes, and the environmental Gini coefficient is calculated by drawing the Lorentz curve. In the case of a certain total amount of flood drainage right, the objective function is to minimize the sum of the environmental Gini coefficients of indicators, and reasonable constraints are set. According to the optimal allocation model of flood drainage right, the optimal allocation scheme of each region is calculated. The results show that after the optimal allocation based on population, GDP and land area is better than the current situation, the environmental Gini coefficients, which are 0. 000 2, 0. 144 1 and 0. 079 6 respectively, are better than the current allocation, and the average variation range of environmental Gini coefficient is 0. 026 3. The allocation model based on the environmental Gini coefficient can consider the actual situation of each region and is conducive to the overall planning of the relationship between urban flood control and regional flood control. On the premise of ensuring the city safety, the optimal allocation of flood drainage right alleviates the pressure of flood control in the Sunan Canal.