The invention discloses a built-in extra-oil-way double-action multistage hydraulic cylinder, and belongs to the technical field of multistage hydraulic cylinders. The built-in extra-oil-way double-action multistage hydraulic cylinder comprises a cylinder bottom, a first cylinder barrel, a second cylinder barrel, a third cylinder barrel, a piston rod, a first integrated valve and a second integrated valve, wherein the second cylinder barrel is coaxially arranged in the first cylinder barrel in a sleeve mode, the third cylinder barrel is coaxially arranged in the second cylinder barrel in a sleeve mode, the piston rod is arranged in the third cylinder barrel in a sleeve mode, the first integrated valve is used for enabling an hydraulic oil to freely flow into an inner cavity of the piston rod from a pipeline connected with hydraulic equipment connected with a driven platform, and the second integrated valve is used for enabling the hydraulic oil to freely flow into the inner cavity of the third cylinder barrel from an oil pipe, The built-in extra-oil-way double-action multistage hydraulic cylinder can be applied to underground working conditions that the reliability requirement of small installation dimension is relatively high, no cable is exposed, and the hose is not connected, and hydraulic power is provided for the hydraulic equipment on the driven platform by arranging additional oil ways in the multistage hydraulic cylinder.