In order to solve the problem of low accuracy of power line extraction of transmission lines with complex terrain and trending, and uneven point cloud density, an efficient method for automatic extraction and reconstruction of power lines was proposed. Firstly, through the space segmentation and point cloud density analysis method, the improved elevation filtering algorithm was used to achieve the rough extraction of power lines; the filtering algorithm based on the average value of the inclination angle between the point clouds was used to extract the power lines precisely; the statistical filtering algorithm was used to complete the extraction of the whole point cloud of the power lines. Then the power lines were separated by the random sample consensus(RANSAC)-based power line striping extraction algorithm, and finally the power line reconstruction was completed by using a model combining straight lines and paraboloids. The results show that the total power line extraction accuracy of this method is 99.342%, and the minimum reconstruction accuracy of a single power line is 0.042m, which is robust to terrain, line direction, point cloud density and other factors. This research provides a reference for power line extraction and 3-D reconstruction of large-scale transmission lines in complex scenarios.