The basic principles and influencing factors of the initial allocation of drainage rights in a basin is analyzed using the existing scarce resource research methods. An index system for the initial allocation of drainage rights is established, and the entropy weight-TOPSIS method is used for the initial allocation of the drainage rights between regions in the basin. The results of the initial allocation of rights are optimized based on the Gini coefficient method. Finally, a calculation example is analyzed for the initial allocation of the drainage rights of the Sunan Canal. The results show that before the optimization of the Gini coefficient, the Gini coefficients of the indices of population, GDP and water area in the region are all close to 0. 4 except the Gini coefficient of annual precipitation index, which is near the unfair interval. After the Gini coefficient constraint optimization, the Gini coefficients of various indices are less than or equal to 0. 3, which is in a relatively fair interval, and the Gini coefficient of the annual rainfall index is also reduced to be 0. 08 from 0. 2 before optimization, which is in an absolutely fair range.