The invention discloses a device for disassembling an oil cylinder. The device for disassembling the oil cylinder comprises a telescopic oil cylinder, wherein the tail end of a cylinder body of telescopic oil cylinder is fixedly connected onto one end of a base through a fixing bracket I; the free end of a cylinder lever of the telescopic oil cylinder is provided with a sliding block; the sliding block is provided with a pin hole used for connecting a cylinder lever of a to-be-disassembled oil cylinder; the base is of a strip groove-shaped structure, and is fixedly connected onto a fixing platform; the other end of the base is provided with a fixing bracket II used for connecting the to-be-disassembled oil cylinder. According to the device for disassembling the oil cylinder, an existing telescopic oil cylinder is adopted to be connected with the to-be-disassembled oil cylinder through the sliding block, the other end of the to-be-disassembled oil cylinder is connected onto the fixing bracket II, and the telescopic oil cylinder is started, so that the disassembly of the to-be-disassembled oil cylinder can be realized; the problems existing in the prior art that waste and old oil cylinders are difficult to disassemble and cannot be recycled are effectively solved; the recycling of components and parts on the waste and old oil cylinders is greatly improved; the procurement cost of equipment is decreased; the economic benefit is improved; moreover, the device for disassembling the oil cylinder has the characteristics of being simple in structure, convenient for assembly and disassembly and low in cost.