Based on the theory of fracture mechanics,the functional relationship between tear energy and fatigue crack growth rate was derived.By transforming the complex multidirectional stress into uniaxial equivalent stress,the fatigue life prediction model of nitrile rubber was established.The MooneyRivlin constitutive model was used to characterize the superelastic behavior of nitrile rubber,and a finite element model was established after simplifying the structure of the DAS combined seal.The location of the dangerous sections was determined based on the stress calculation results.The stressstrain relationship of nitrile rubber was obtained by fitting the tensile test data,the change of tear energy was calculated by numerical analysis method,and the crack initiation position and fatigue life were predicted.It is found that dangerous section position of the DAS combined seal is near the chamfer of the right seal groove.The position and fatigue life of the dangerous sections predicted by the simulation software are consistent with the theoretical calculation results,which verifies the correctness of the theoretical calculation results.