Abstract: A set of equipment for the step linear output control was researched in the paper.The hydraulic cylinder of the equipment can output linear displacement by a special hydraulic valve and step motor control.It can also convert date input to mechanical displacement with a large drive force without D/A.The study indicated the key of the hydraulic valve design and introduced the mathematical model of the control system and the PID control system of the single chip microcomputer control.The results proved that the linear output equipment of step motor control had better linearity and realizes the control mode easily.There is no obvious hydraulic lock and the system reliability is greatly improved.