The key to enhance the precision of sheet metal stamping parts is accurate prediction and control of the springback. And one of the dominant factors of springback is the elastic modulus. The change of elastic modulus with plastic deformation was experimentally studied for the annealed LY12 and the annealed LF21 aluminum alloy respectively, and the changing role of elastic modulus with plastic deformation was obtained. By inverse pole figure from the X-ray diffraction analysis, the effects of the material original textures and their changing with plastic deformation on the elastic modulus were studied. And by positron annihilation lifetime spectrum , the influence of lattice distortion caused by crystal defect during plastic deformation on the elastic modulus was investigated. The micromechanism of the elastic modulus changing with plastic deformation for aluminum alloy is revealed, which lays a foundation for improving the stamping parts’ precision.