Abstract: The microstructure and mechanical properties of Al-1.2Si-0.5Mg cold rolled alloy with 0-75% different deformations were investigated by metallography microscope, transmission electron microscope, hardness test and tensile test.The results show that with the increase of cold rolling deformation amount, the Al-1.2Si-0.5Mg alloy grains are gradually elongated along the rolling direction, the size of precipitated phase gradually decreases, and the number of precipitated phase gradually increases.When the cold rolling deformation amount reaches 75%, the alloy grain is completely broken.With the increase of cold rolling deformation amount, the hardness and strength of Al-1.2Si-0.5Mg alloy gradually increase, while the plasticity gradually decreases.The hardness and strength of the 75% cold rolled Al-1.2Si-0.5Mg alloy reach the peak, the hardness, tensile strength and yield strength are 118.3 HV, 336.4 MPa and 264.5 MPa respectively, and the elongation of the alloy is 17.1%.