In order to analyze the sealing performance of the hydraulic cylinder piston rod Y-ring in deep sea environment,the simulation model of the Y-ring was established by using ANSYS software,and the sealing stresses of the piston rod Y - ring were analyzed under different working conditions.The results show that during the process of diving from the sea surface to the 5 km deep sea,the maximum von Mises stress is basically unchanged and the maximum contact stress increases by about 37% under the three working states,such as installation,piston rod extension and retracting;with the increase of compression ratio,the maximum contact stress decreases,and the maximum von Mises stress changes inconsistent.The hydraulic cylinder piston rod Y-ring seal structure designed according to the existing standard meets the requirement of deep sea sealing.