Abstract: Laser drilling is a complex physics process, which involves multiple material state transformation.In order to simulate the process,the material's state transformation change with heating time is equivalent to the change of power density distribution change with time in the infinite medium.Based on the analytic solution of thermal diffusion equation of the infinite medium with constant thermal physical properties, approximate mathematics expressions of laser drilling were formulated.Corresponding software was edited to simulate drilling process.The simulation computation shows that the designed software can simulate a logical process of the cavity formation.If the computation parameters are changed,the holes with different shapes will be obtained.The investigation can used to improve the laser processing technology and provide a fast and efficient tool to estimate thermal damage induced by the laser irradiation.