Abstract: T6 heat treatment was conducted on A356 aluminum alloy, whose aging process was carried out under 33 mT low intensity pulse magnetic field. The effects of aging temperature (175,185 ℃) and aging time (50, 60, 70 min) on the microstructure and mechanical properties of A356 aluminum alloy were studied. The results show that after aging under pulse magnetic field, the secondary dendrite spacing of A356 aluminum alloy decreased with the increase of aging temperature or aging time, and the aspect ratio of eutectic silicon decreased first and then increased with the increase of aging time. The size and aspect ratio of eutectic silicon at 185 ℃ aging temperature were higher than those at 175 ℃, but the quantity decreased. After aging under pulse magnetic field, the tensile strength and yield strength of A356 aluminum alloy increased with the increase of aging time or aging temperature. The improved heat treatment process for A356 aluminum alloy was solid solution at 540 ℃ for 60 min+aging at 175 ℃ for 70 min, and during aging applying 33 mT pulse magnetic field. Treated by this process, the tensile properties of the aluminum alloy met the reguirements.