The machine of remove risers how it works was described.According to the design principles and design requirements,a control method of hydraulic system was proposed based on multiactuator sequential action.The requirements of each actuator of the hydraulic control system were analyzed,and rationaly chosed and improved design of the hydraulic sequential control loop,speed control loop,lock loop and valvecontrolled hydraulic cylinder servo control loop,and others.Loops were mutually related to each other and mutually independent of each other at the same time.The design not only greatly improves the automation degree of the system,stability and reliability,but also improves the maintainability of the system.