Based on the heat conduction equation, a theoretical model related to the excimer laser irradiation of ZnO thin films is built. The thermal effect in the KrF excimer laser irradiation of ZnO thin films is simulated and analyzed. The distributions of temperature field and thermal flux of the films are calculated. The variation relationship between temperature and time during the laser action process is discussed. The influence of the laser energy density on the temperature field of the films is analyzed. The simulation results show that the excimer laser annealing process of ZnO thin films has the heat quench characteristic, the surface temperature of ZnO thin films increases linearly with the laser energy density, and the thermal melting threshold of film surfaces is 261 mJ/cm2.