In order to reduce the potato harvest cost,the hydraulic system of the photo lifting and transportation was designed.Based on the working feature of hydraulic system,the pressure and flow characteristic of the mechanism arm and motor driving conveyer belt for the system were analyzed when the speed of the tractor was 1 500 r/min.The results show that the hydraulic system flow of the first stage mechanism arm is basically maintained at 30 L/min.The pressure and flow of hydraulic motor change greatly at the motor start stage because overcoming the static friction of the system.However,the flow of hydraulic motor will arrive to stable state when the conveyer belt operates stably.