Abstract: In order to facilitate follow-up filtering of the airborne LIDAR points cloud,we presented two preprocessing methods.One is the mean-tolerance method for preprocessing the forested areas with dense vegetation and steep slope;the other one is the angle-tolerance method for preprocessing the urban areas with dense laser footprints reflected from walls of buildings.Two datasets with different characteristics were used in experiments to test the two presented preprocessing methods.The experimental results were analyzed qualitatively and quantitatively.The results indicate that two preprocessing methods are effective,two types of filtering errors are reduced when filtering with preprocessing.