Aiming at the problem of low accuracy of open loop control of multi-joint hydraulic manipulator, a set of closed loop control system of hydraulic manipulator based on 51 Micro Controller Unit (MCU) control is designed.Control data was input on the graphical interface of the upper computer, and communicated to the 51 MCU through the serial port, to drive movement of manipulator by controlling on and off of electromagnetic valve.At the same time, according to the real-time motion Angle of each joint collected by the photoelectric encoder, the MCU was carried on the feedback control.It reduces the motion error of the manipulator, and forms a closed loop control system.