The viscoelastic behaviors of O-ring rubber seal in floating oil seal structure was studied by theoretical calculation and finite element simulation.It is found that the sealing pressure is decreased gradually with the increasing of time during relaxation process and creep displacement is increased gradually during creep process.Both relaxation and creep process of O-ring in floating seal can lead to the oil leakage for floating seal structure.The results of theoretical model are consistent with those of finite element analysis,which proves that the established finite element analysis method can be used to predict the load and displacement changes of O-ring in floating seal in the process of relaxation and creep.A new floating oil sealing structure composed of PTFE gaskets and constant force springs was proposed in view of the structure relaxation and friction damage of O-ring in floating oil seal structure.