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Aiming at the problem of insufficient hydrodynamic force in the small branching river in the plain river network, a flapping-wing bionic water pumping device was designed, by controlling flapping wings to complete the two degree of freedom coupling motion of heave and pitch, the water in the closed channel was mechanically pressurized, achieving one-way pumping of water, to meet the demand for large flow and high efficiency water transmission under very low head conditions. A flapping-wing model was established based on the tuna tail fin and rectangular flat plate. The finite volume method (FVM) and overlapping grid technology were used to carry out three-dimensional numerical simulation of flapping hydrofoil with different characteristic chord lengths and contours, and the pump water test of tail fin and rectangular flapping hydrofoil was compared. The results showed that with the increase of the characteristic chord length of the flapping hydrofoil, the average thrust coefficient in the cycle was increased, corresponding to an increase in the vortex strength of the wake region vortex ring. However, its pumping efficiency was slightly decreased. Under the same area constraint, the flapping hydrofoil with the characteristic profile of the tail fin improved the pumping flow and efficiency of the device compared with the rectangular flapping hydrofoil. When the test flapping frequency was 0.7Hz, the stable average flow rate of the tail fin flapping hydrofoil flow field was 28.44cm/s, which was 13.6% higher than 25.13cm/s of the rectangular flapping hydrofoil.