Because the depth information of pavement could not be got directly by traditional method of pavement detection, a detection method for the depth of broken block in pavement based on 3D laser scanning technology was presented. The point cloud data of the broken crack can be obtained by a 3D laser scanner. The crack data can be divided into several slices along the horizontal direction, and the depth information for each of the slices can be estimated by the distance between the up and down planes respectively. According to the practical engineering, a novel plane fitting iterative algorithm based on dynamic threshold was proposed, it can not only identify and remove invalid points in the point cloud data effectively, but also accomplish plane calculation with errors in three directions. Experiments show that the proposed method can not only get the depth information of the whole pavement broken block, but also reflect the change trend of the depth of the broken block along the horizontal direction.(310824150011)