Abstract: For angular complement of coupling, alternative stresses are generated in the membrane while the coupling rotates. The alternative stresses cause fatigue problem. So the fatigue life should be considered For circular membrane with six holes and width varying circular membrane, the finite element method and thin plate bending theory are used to establish the computational models of stresses. The improved local stress-strain method is introduced to evaluate the crack initiation and life of membranes. The stresses in circular membrane and width-varying circular membrane, additional loads and fatigue life are analyzed. The results show that the fatigue life of reasonably designed membranes can satisfy the service need of rotor system.