1. Piston type A single piston rod hydraulic cylinder has a piston rod at only one end.This is a single piston hydraulic cylinder.The inlet and outlet A and B at both ends can pass pressure oil or return oil to realize two-way movement, so it is called double-acting cylinder. The piston can only move in one direction, and its opposite direction must be completed by an external force.But its stroke is generally larger than that of piston hydraulic cylinder. Piston type hydraulic cylinder can be divided into single bar type and double bar type of two structures, the fixed way by the cylinder block fixed and piston rod fixed two kinds, according to the action of liquid pressure has single action type and double action type.In the single-acting hydraulic cylinder, the pressure oil is only supplied to a cavity of the hydraulic cylinder, and the cylinder realizes the single-direction movement by the liquid pressure, while the counter-direction movement is realized by external forces (such as spring force, dead weight or external load, etc.).The movement of the piston in two directions of the double-acting hydraulic cylinder is completed by the action of liquid pressure through the alternating oil inlet of two Chambers. 2. Plunger type (1) The plunger type hydraulic cylinder is a single acting hydraulic cylinder, hydraulic pressure can only achieve a direction of movement, the return trip of the plunger depends on other external forces or the weight of the plunger; (2) The plunger is supported only by the cylinder liner and does not contact with the cylinder liner, so the cylinder liner is easy to process, so it is suitable for doing long stroke hydraulic cylinder; (3) The plunger is always under pressure when working, so it must have sufficient stiffness; (4) The weight of the plunger is often large, when placed horizontally, it is easy to sag due to self-weight, resulting in unilateral wear of seals and guide, so its vertical use is more favorable. 3. Telescopic type The retractable hydraulic cylinder has two or more levels of piston, the piston in the retractable hydraulic cylinder from large to small, and no load retractable order is generally from small to large.Telescopic cylinder can achieve a longer stroke, while the length of retraction is shorter, the structure is more compact.This kind of hydraulic cylinder is often used in construction machinery and agricultural machinery.There are multiple pistons in one motion, each piston successive motion, its output speed and output force are changed.