The invention relates to a spring-based hydraulic device and a method for suspending a riser string. The device comprises an upper disk of a cyclic structure, a lower disk of the same cyclic structure arranged oppositely to the upper disk, a plurality of telescopic pins evenly distributed along the inner edge of the upper disk, two or more than two high-pressure upright columns arranged between the upper disk and the lower disk, and two or more than two common upright columns arranged between the upper disk and the lower disk, wherein each high-pressure upright column comprises a hydraulic cylinder, the bottom end of the hydraulic cylinder is fastened to the top surface of the lower disk, a piston rod is inserted into the hydraulic cylinder, the top end of the piston rod is fastened to the bottom surface of the upper disk, and the upper and lower cavities of the hydraulic cylinder are full of a high-pressure liquid; each common upright column comprises an outer barrel, an inner barrel located inside the outer barrel, a piston arranged at the bottom end of the inner barrel, and a high-strength spring sleeving the outer barrel and the inner barrel, and wherein the bottom end of the outer barrel is fastened to the top surface of the lower disk, the top end of the inner barrel is fastened to the bottom surface of the upper disk, and the top end of the high-strength spring props against the bottom surface of the upper disk, while the bottom end of the high-strength spring props against the top surface of the lower disk.