Abstract: Non-contact optical measurement system based on three-dimensional digital image correlation (3D-DIC) was established to test the elastic constants of 2A12 aluminum alloy. The effects of different sizes of DIC parameters, i.e. subset size and step size, on the elastic constant test results of the material were investigated, and the deformation evolution law of 2A12 aluminum alloy under the action of tensile load was also discussed. The results show that the elastic modulus and Poisson ratio of three groups of 2A12 aluminum alloy specimens were 66.32, 67.51, 63.08 GPa and 0.333, 0.336, 0.347, respectively. Changing the subset size caused the change of image noise, subset size had more influence on the test results compared to step size, and step size mainly controlled the computational time of DIC algorithm. The 2A12 aluminum alloy specimen fractured after three stages of elastic deformation, uniform plastic flow and strain localization.