Rotary blades used in many structures are inevitably exposed to variable amplitude loads that cause fatigue and deterioration of their strength over time. In the present study the fatigue behavior of a composite blade consisting of aluminum spar and composite laminate under the influence of variable amplitude aerodynamic loads has been evaluated. This evaluation has been based on the philosophy of safe life fatigue design. First, the loads acting on the blade have been extracted during different operating conditions. Then, by applying these loads to the FE model of the blade, the stress (or strain) components in metal and composite parts of the blade have been obtained. Finally, based on the stress (strain) components obtained for each of the model elements (in different flight conditions and rotation angles), the fatigue damage accumulation parameter of the aluminum spar and each of the equivalent layers of the composite shell have been calculated. The results have shown that the fatigue damage in both the aluminum spar and most of the composite layers is higher near the blade root, which is necessary to pay attention to in the design of this structure. In addition, the methodology of this evaluation is also introduced.