In order to promote and apply non-contact video extensometer to the mechanical test of materials, the tensile testing of 2A12T4 aluminum alloy profile sample is conducted on the 20kN electronic universal testing machine by automatically measuring elongation and width of the deformation for the alloy in non-contact video extensometer. At the same time, electronic strain extensometer is installed in the length direction for tracking measurement, with keeping in the corresponding force value, cut deformation in the width direction is measured by means of micrometer measurement . After the sample cracks, the tool microscope is used to measure the deformation in both length and the width directions. The deformations measured by two groups of measuring tools are compared with each other, and the average value curves in the absolute deviation for the vertical and horizontal deformations are drawn. The analytic results indicate that using non-contact video extensometer to measure mechanical properties of materials is able to completely meet the needs of production and test.