An improved device for an adjustable stroke cylinder includes a cylinder and a sleeve. The cylinder includes a cylinder body and a piston rod movably connected to the cylinder body;the sleeve is hollow and has threads on its outer surface, and a first nut and a first nut are threadedly connected to the sleeve. The second nut, the sleeve is sleeved on the piston rod and the first end of the sleeve is connected to the tail of the cylinder. The end of the piston rod protrudes from the second end of the sleeve. There is a guide groove on the sleeve;the piston rod is mounted on the second nut. A guide limit pin is provided. The guide limit pin slides along the guide groove. The guide limit pin is located between the first nut and the second nut. The guide limit pin protrudes from the outer peripheral surface of the sleeve and can resist the first nut and the second nut. The second nut. This utility model can adjust the forward motion stroke and the backward motion stroke by setting the guide limit pin, the first nut and the second nut, and when the cylinder loses air, the advance and retreat can be manually controlled by adjusting the nut, thereby driving the corresponding The mechanism advances and retreats manually.