This paper present a power lines automatic extraction method from airborne LiDAR point cloud. Firstly, ground points are removed by automatic filtering method based on fluctuant feature of terrain. Vegetation points, building points and part pylon points are also removed by dimensionality feature and direction feature. Secondly, 2D Hough transform and least square fitting are used to fit center line equation of power lines. And then, the laser point of each power lines can be obtained by center line equation. In this step, power lines projection overlap in the horizontal plane are considered as well. Finally, block centroid calculation method is used to calculate 3D nodes of each power lines. These nodes are used to output the power lines vector. The experimental result shows that the proposed method can extract complete power lines from airborne LiDAR point cloud. This method has some practical meaning for power line inspection.