The technology of laser drilling rock has wide applied future in petroleum industry, but there are few mechanism researches of laser to rock interiorly. This thesis analyzed the temperature distribution of the sandstone under the laser with uniform and Gaussian intensity according to the instability heat transfer theory, then simulated the heat stress distribution and the minimum laser intensity to drill sandstone according to the stress equation and boundary condition. The fusion and gasification model was constructed according to the law of conservation of energy and the fusion and gasification speed at certain laser power was calculated. The simulation results show that the speed of laser drilling rock is much faster than mechanical revolving aiguilles technology in deep oil well and has prominent industrial application potential.