A numerical method is presented to determine the dynamic stresses and fatigue life of a flutter blade in turbomachinery.The method contains the calculation of unsteady aerodynamic work and damping work of the vibrating blades;the conception of equilibrium amplitude;and the estimation of its fatigue life in accordance with the dynamic stresses of the vibrating blades under the equilibrium amplitude.The unsteady aerodynamic work is obtained from the calculation of 3-D unsteady N-S equations with the Oscillating Fluid Mechanics Method (OFMM) and the Parametric Polynomial Method(PPM).The maximum kinetic energy and dynamic stresses of the vibrating blades are calculated with FEM.The fatigue life of the blade is estimated with Manson-Coffin Equation.The calculated results demonstrate that the blades can operate even the unsteady aerodynamic work is positive.