Abstract: Effect of aging treatment on the tensile properties, microstructure and fracture characteristics of Al-Li alloy were studied by tensile testing, SEM and TEM. The results show that, with the increase of aging time, the strength of short-transverse direction increases quickly and the elongation decreases rapidly. The fracture mode changes from the mixture of transgranular and intergranular cracking to intergranular cracking. Abundant T₁ phase precipitates in grains during aging process, which enhances the strength and restraining the matching deformation within grain, leading to intergranular cracking during tensile test.