Laser rock-breaking technology is a new type of non-contact rock-breaking technology, which is one of the most promising technologies to replace the traditional methods. At present, the research on laser rock-breaking technology mainly focuses on the rock-breaking mechanism and parameters optimization under the continuous laser, while the research on the law of damage process of rock under the pulse laser is relatively lacking. Therefore, in this paper, pulse laser rock-breaking tests with laser power (400W and 800W) and irradiation time (4s, 8s, and 12s) were carried out. The damage morphology and quality of the rock before and after the tests were measured and compared, and the damage performance of the rocks under different powers was analyzed. The test results show that the diameter of the ablation pit of 800W is 2.5% larger than that of 400W on average at the same moment. The depth of the ablation pit of the former is about 1.5 times that of the latter, and the mass damage of the former is about twice that of the latter. On this basis, a three-dimensional model of pulse laser rock-breaking based on the discrete element method was established, and the evolution law of granite ablation pits and cracks under pulse laser irradiation was investigated. The simulation results show that the diameter and depth of the ablation pits increase with time, and in general, both show a non-linear growth pattern with time. The crack development is dominated by radial development at the early stage, and the radial development rate is 3.1 times the development rate of the axial direction. The volume of thermal cracking damage increases exponentially with time, and the overall damage form of the rock tends to thermal cracking damage with time. The results of this study are of guiding significance for pulse laser rock-breaking drilling.