To evaluate the flood control impact of sand mining project on embankment project of large aircraft in Nanchang ,based on the characteristic of on tail reach of the lower Ganjiang River，combined with the requirements of the sand mining project in river，2D hydraulic model was used to solve and calibrate water level, flow rate, and other factors at the mining area. The results show that after the project is implemented, because the design of the case is under lake flood control , so its biggest lowering of water level is 0.017m, the maximum change of flow rate is within 0.20m /s, the flow dynamic axis only have a local adjustment in the mining area. It is indicated that the sand mining project had a partial, limited influence on the flood control safety.