Abstract: The principle, structure and parameters of the diode-laser lidar used to measure visibility were introduced, and a steady iteration algorithm was proposed to calculate the extinction coefficient. The intercomparison experiment with this lidar and the Belfort model 6230A made in America was conducted for horizontal and slant visibility detection. The results show that the possibilities of average relative error below 10%, 20% and 30% for horizontal visibility measurements are 45.6%, 84.7% and 91.2%, respectively. For slant visibility measurement, the change of the visibility is obvious, which demonstrates the difference and significance of the slant and horizontal visibility measurements on various weather conditions. It is sufficiently shown that this lidar system is capable of measuring t