Fatigue property of Al-Li alloy after various heat treatment was investigated. The results show that the fatigue strength is enhanced with the age hardening progressing. Compared to the solution treated specimen, the fatigue limit is improved to 136% for sub-ageing treated specimen and 155% for peak-ageing treated specimen, respectively. In the meanwhile, the fatigue deformation becomes non-uniform with age hardening progressing. The fatigue cracks initiate and propagate prior from the un-uniform slip band, causing transgranular fracture or the mixed mode of transgranular fracture and intergranular fracture.