At present,the mechanized harvest of lotus roots is low,the labor intensity of workers is high,and the harvesting efficiency of lotus roots is low. Therefore,a walking hydraulic scour type lotus root digging machine was designed. Hydraulic system was used to control the reciprocating movement of sewage submersible pump and nozzle. Two sewage submersible pumps were used to control one nozzle respectively to make the water flow have enough flow and pressure. The hydraulic control system was simulated and analyzed by AMESim,it was found that the hydraulic system works well through the adjustment test of the hydraulic system. In addition,a BoxBehnken test was carried out,and the response surface analysis and parameter optimization analysis were carried out,where the jet angle of the nozzle,the depth of the nozzle into the mud and the moving speed of the hydraulic cylinder for pushing were taken as the test factors,while the scour depth and the floating rate as test indexes for design. The experimental results show that when the jet angle of the nozzle is 30°,the depth of the nozzle into the mud is -24 mm,and the moving speed of the hydraulic cylinder for pushing is 10 cm/s,the scouring performance of the machine reaches the optimal state，at this moment the scour depth is 302 mm,and the floating rate is 90%.The research can provide reference for the design and optimization of the lotus root digging machine.