To improve the filtering effects of point clouds in abrupt terrains, a filtering algorithm is proposed based on dynamic thresholds. This algorithm can be divided into two stages. The first filtering aims at obtaining the more accurate ground points, while the second filtering aims at obtaining the elevation difference thresholds in different regions based on the ground points obtained by the first filtering. Subsequently the original point clouds are filtered according to the above thresholds. The experimental results show that the proposed algorithm can be used to obtain the smaller Type Ⅰ error and total error, comparing with the other classic algorithms. Moreover, this algorithm can be used to filter the ground objects and simultaneously protect the terrain details effectively.