Double-acting multi-stage telescopic oil cylinder

The invention relates to a double-acting multi-stage telescopic oil cylinder which solves the problem of longitudinal machining of an oil duct hole in the wall of a cylinder barrel of a traditional double-acting multi-stage telescopic oil cylinder. The double-acting multi-stage telescopic oil cylinder comprises a base, an outer cylinder barrel, a middle cylinder barrel, an inner cylinder barrel, an inner oil pipe, a first end cover, a second end cover and sealing assemblies (8 to 16). Rodless cavities are communicated with each other through an axial oil hole G in the first end cover of the middle cylinder barrel. Cavities with rods are communicated with each other through a radial oil duct E on the middle cylinder barrel, a radial inner oil duct C on the first end cover and an inner oil duct D formed by the inner oil pipe fixed to the first end cover and a radial oil duct F on the side wall of the inner cylinder barrel. The double-acting multi-stage telescopic oil cylinder is compact in structure, the internal hydraulic loop is reasonable and clever in arrangement, machining and manufacturing are relatively easy, and manufacturing cost is low.