The invention discloses a hydraulic scaling mechanism of sealed cylinder body on the basis of flexible element, which is composed of a piston connected with a movement input end, a piston connected with a movement output end and hydraulic cylinders with different calibres, wherein the hydraulic cylinder is filled with hydraulic fluid. The hydraulic scaling mechanism is characterized in that the outer surfaces of the piston connected with a movement input end and the piston connected with a movement output end are both covered by the flexible element which covers one side of the piston, which is provided with hydraulic fluid. The structure of the hydraulic scaling mechanism is the cylinder body based on cylindricity and adopts a flexible element to replace the traditional hydraulic piston to confine hydraulic fluid in a sealed space. The hydraulic scaling mechanism has simple structure, low cost and simple maintenance. Because the flexible element is adopted, the hydraulic scaling mechanism utilizes the favorable flexibility and strength of the flexible element, favorable sealing performance, excellent anticorrosion capability and the like to form a sealed hydraulic mechanism; the hydraulic mechanism does not have sliding friction when working, thus solving the problems of sliding friction, low-speed crawl, seal leakage and the like existing between the piston and the cylinder body of the traditional hydraulic mechanism.