Aiming at the problem that the maximum range of the laser rangefinder changes significantly under different atmospheric conditions, the relationship between the apparent optical parameter atmospheric visibility V and the atmospheric absorption coefficient, scattering coefficient and total attenuation coefficient are established, and the Monte Carlo method is used to simulate the laser atmospheric transmission process. The long-range laser rangefinder of Voxtel Corporation of the United States is taken as an example to quantitatively calculate the influence of visibility on the maximum range in foggy environment. The results show that the laser rangefinder with a nominal maximum range of 10 km has a maximum range of 30 m, 335 m and 1 240 m under the environmental conditions of 20 m, 300 m and 1 500 mm of visibility, respectively. And the maximum range of rangefinder will change obviously along with the change of meteorological conditions. This simulation method evaluates the influence of atmospheric optical parameters on the laser rangefinder range and guides parameter optimization in the system design process.