The stress-strain curve in the large plastic deformation process is always not available due to the strain gauge deficiencies in large deformation measurement. Considering this problem, digital marker identification technique is used to measure large deformation of Steel Q235 with images taken by with charge-coupled device. Then together with the deformation measured by traditional stain gauge at small deformation stage, the total stress and strain curve is obtained at macroscale. The mesoscopic deformation is measured by a material testing system assembled with scanning electronic microscope. The images from the initial stage to the rupture stage are captured synchronously. What’s more, using the grid method, the strain and rotation in rational mechanics is analyzed.