U-shaped seal ring is a kind of seal structure commonly used in liquid rocket engine,and its sealing performance is the key factor to determine the reliability of the engine.In order to study the U-shaped ring sealing mechanism and improve the sealing performance of the overall structure,the finite element analysis model of U-ring seal structure was constructed,and the sealing performance of the sealing ring was analyzed under normal temperature pretightening and low temperature working conditions.It is found that compared to the pretightening condition at room temperature (20 ℃),the effective contact width and contact stress of the U-shaped ring sealing surface are larger under low temperature (-183 ℃) working conditions,but there is still an issue of insufficient contact between the sealing surfaces.The interface of U-ring seal was optimized by the optimization design method of seal interface morphology.After optimization,the U-shaped ring sealing surface changes from a flat morphology to an uneven and non-linear morphology.Under low-temperature working conditions,the effective contact width of the U-shaped ring sealing surface is increased by 138%,the uniformity of contact stress distribution is improved by 99%,the effective contact width of the sealing surface is increased significantly,and the uniformity of contact stress distribution is improved significantly.The overall sealing performance of the structure is significantly improved.