Abstract: On the offshore jack-up drilling platform built in the 1980s, the piston rod of the hydraulic cylinder of the lifting device often produces scratches and failures, which affect the normal operation of the hydraulic cylinder. The inspection found that the inner diameter of the packing gland of the hydraulic cylinder was small, and the packing gland was in contact with the piston rod, resulting in scratches on the piston rod. The paper describes the structure and measurement data of the hydraulic cylinder, optimizes the inner diameter size of the hydraulic cylinder packing gland, optimizes the original design size \; \phi 400_ + 0.120^ + 0.280 to \;\phi 401_ - 0.05^ + 0.05, determines the reasonable inner diameter size and tolerance of the packing gland, and solves the problem of scratches on the piston rod of the hydraulic cylinder. It ensures the normal operation of the jack-up drilling platform lifting device.