Aimed at the special working condition of the watercooled cylinder,such as,carrying out cold and hot interaction under high temperature difference,realization of dynamic and static sealing under high speed,ensuring no leakage under high pressure,and etc.,the design requirements of seal structure of watercooled cylinder were analyzed.The higher reliability design scheme was taken for the structure design and the choice of seals.Aimed at the problem of dynamic seal in special working conditions,different material were adopted for two kinds of U seal matching of the using scheme,thereby both the compressive capacity and the wear resistance of rotary sealing structure were considered.Test results show that the safety design of the sealing structure is feasible for the special conditions of watercooled cylinder,which provides a new method for solving this similar engineering sealing problem.