The particular geometric shape of the buffalo hoof is suitable for walking on the paddy-field and has low resistance during working. The bionic information of the buffalo hoof was extracted by reverse engineering technology, and then the bionic blade for paddy-field impeller was designed. To guide the design of paddy impeller, the mechanism of performance improvement of bionic blade was studied by numerical simulation. The simulation results show that the fluid medium impact and separation of blade surface fluid velocity mutation can be delayed by the bionic shape effectively. The bionic shape can reduce impact endurance test resistance of the separated flow, and improve the driving force of impeller. Moreover, the bionic blade may increase its driving torque.