Abstract: To evaluate the maximum range of laser rangefinder quantificationally, and to get the performance in different visibility rapidly, a new numerical algorithm was put forward. The empirical formula of atmospheric transmissivity was plugged into laser range equation, so a transcendental equation was generated and solved, the maximum range was calculated correspondingly. Based on the numerical algorithm, proportional method was applied to deduce maximum range in different visibility. The numerical simulative calculation of maximum range in different conditions was made by using this theory, and relation curves between maximum range and different visibility(Rmax-V) were drawn to explain the influence of visibility on maximum range visually. The simulation results show that the new numerical algorithm works well in calculating the maximum range of laser rangefinder. It has many virtues, such as quantitative results and high precision, etc. It provides a new approach to evaluate and assess the maximum range of laser rangefinder in lots of different situations.