Hydraulic Cylinder is an executive element in a hydraulic transmission system. It is an energy conversion device that converts hydraulic energy into mechanical energy. The hydraulic motor realizes the continuous rotation movement, while the Hydraulic Cylinder realizes the reciprocating movement. Hydraulic Cylinder has three types of structure: piston cylinder, plunger cylinder, and swing cylinder. The piston cylinder and plunger cylinder realize reciprocating linear motion, output speed and thrust, and swing cylinder realizes reciprocating swing, and output angular velocity (rotation speed) and torque. In addition to using the Hydraulic Cylinder individually, it can also be used in combination with two or more or with other mechanisms. To complete special functions. The hydraulic cylinder is simple in structure and reliable in work. It has been widely used in the hydraulic system of machine tools.