Based on DIC(digital image correlation) technology, the whole field displacement of concrete subjected to uniaxial compression after 20, 200, 400, 600， 800℃ was observed. The variation characteristics of the strain nephogram and the variation law of the deformation parameters of concrete at different temperatures and different loading stages were analyzed. The results show that 400℃ is the critical temperature for the matching of the transverse strain concentration region and the maximum longitudinal strain compression area of concrete. Gr H (the slope corresponding to the origin of the transverse stress strain curve to the rising 04fcθ, fcθ is peak strain under temperature θ) is more sensitive to temperature than the elastic modulus Eθ. High temperature damage will lead to large volume compression of concrete at lower stress ratio.