Abstract: The technical principles of video extensometer and digital image correlation (DIC) technology were introduced, with the applications including the real strain measurement upon the virtual gauges, the analysis of the local strength and plasticity, the direct characterization of the strain trace (Luders effect). Moreover in comparison with the drawbacks of plastic strain ratio r value measurement by regular electric transversal extensometer, a new optical measurement solution to determine the r value with high reproducibility and reliability was proposed, by employing the averaged transversal strain to calculate r value, and through monitoring the width change of specimen contour or the real measurement upon several pairs of virtual initial transversal gauges by two-dimensional DIC technology.