Abstract: The fatigue crack propagation(FCP) rate of 6156 aluminum alloy in various aging states were studied. In addition, the effects of different stress ratios(0.1, 0.5) and orientations(L-T, T-L)in same aging states on FCP rate also were investigated. The microstructure and fracture morphology of the alloy were examined by using TEM and SEM. The results show that nature-aged alloy had the mininum FCP rate, followed by under-aged alloy in T6 in the first stage and the second stage of fatigue, and over-aged alloy in T6 had the largest FCP rate, while peak-aged alloy in T6 was between under-aged alloy and over-aged alloy in T6. The fatigue crack propagation rate of stress ratio 0.5 was bigger than that of stress ratio 0.1. Orientations had little effects on the fatigue crack propagation, 6156 aluminum alloy had not obvious anisotropic of fatigue property resistance.