Abstract: A two-dimensional transient physical model of flat-topped laser irradiation Germanium was established based on heat conduction theory and thermoelastic dynamic theory. The thermodynamic field of the irradiated material was simulated to compare the thermodynamic field differences at different irradiation times. The distribution of temperature field and stress field gradients along radius was discussed, as well as the impact of irradiation time on the distribution. The calculation results show that the greatest temperature rise effect occurs at the center of target material, and the temperature goes up as the irradiation time extends, moreover, stress field peak occurs outside the spot radius.The temperature and stress field gradients reach maximum values at the spot edge, and the longer the irradiation time, the greater the temperature and stress fields gradients at a fixed point. Under the given conditions , the damage time of subject material was calculated, and the stress damage threhold was reached first.