Abstract: The changes of hardness and microstructure of three aged Al-Cu alloys contained precipitates θ″, θ′ and θ during multi-axial compression (MAC) at room temperature were investigated by hardness tester, X-ray diffraction and transmission electron microscopy. The results show that with the increase of compression pass, the hardness of three aged alloys gradually increased, the hardness values of specimens containing θ″ and θ′ phases appeared a valley. The alloys containing θ″ and θ′ phases obtained equiaxed ultra-fine grains, whose size was 0.56-0.71 μm. And the alloy containing θ phase obtained slender grains, the precipitates seldom redissoluted.