According to the maintenance requirement of power transmission line, a power transmission line corridor cleaning method based on UAV LiDAR technique is proposed. Firstly, the adaptive filtering method is used to separate UAV LiDAR point cloud data of the ground. Then, the transmission and grounding lines, tower, and typical ground objects are classified based on the dimensional features and directional features which composed of the singular value of the covariance matrix composed of the point sets in the neighborhood of the point cloud. After that, transmission line 3D model is constructed through catenary equations, and the distance between ground objects and transmission line conductors in transmission corridors are calculated based on the mesh generation method. At last, according to the regulations, the clearing area can be calculated automatically for trees and buildings that do not meet the requirements of safe distance. The accuracy and effectiveness of the proposed method are verified by comparing the results of automatic calculation and manual calculation analysis. The results show that the proposed corridor cleaning method has the characteristics of lower error and high efficiency, which is beneficial to the operation and maintenance of transmission lines.