In order to study the atmospheric transmission characteristic of 1.54 μm and 1.06 μm lasers and the impact on laser ranging, Modtran is used to simulate the atmospheric transmittance of 1.54 μm and 1.06 μm lasers in different conditions which include atmospheric molecules, aerosol and fog. The laser ranging principle is used to get the relationship between the maximum range of pulse laser rangefinder and atmospheric transmittance. The results point out that, the impact of atmospheric molecules is negligible. Decrement of aerosols to 1.06 μm laser is heavier than that to 1.54 μm laser, and humidity is the key factor. Fog has very heavy decrement to both of the lasers, and they have almost the same atmospheric transmittance in fog. The reduction of visibility has heavy impact to the maximum range of pulse laser rangefinder. Since 1.54 μm laser has better atmospheric transmittance than 1.06 μm laser, pulse laser rangefinder which uses 1.54 μm laser has advantage in the aspect of maximum range.