In order to improve the working reliability of pressure controller in the pressure core sampling for the seafloor drill, the challenges faced by the pressure controller in the working phase are analyzed. The working parameters of Y-ring on the pressure-retaining performance are analyzed. The optimization scheme of the working parameters for Y-ring is obtained and verified by sea trial. The conclusions are as follows: The gap extrusion degree of Y-ring is proportional to the working pressure. When the working pressure exceeds 20 MPa, the increase rate of the maximum contact stress increases. Under the condition that the friction coefficient is 0.1–0.4, the safety margin of the maximum contact stress is proportional to the friction coefficient. When the friction coefficient increases from 0.4 to 0.5, the safety margin decreases. Under the condition that the interference is 0.66–0.76 mm, the growth rate of the maximum Mises stress is slow. when the interference is 0.7 and 0.76 mm, the safety margin decreases. When the extrusion gap is 0.4–0.6 mm, the increase trend of safety margin is more obvious. When the extrusion gap is 0.6 mm, the growth rate of the maximum Mise stress increases. The success rate of the sealing cap installation is about 80%.