Abstract: Laser point cloud data has gradually been applied in automatic grid inspection and auxiliary safety maintenance. Extracting topological information quickly from large-scale point cloud data and applying it to live-line work planning has significant application value and engineering challenges. This research proposes a method for measuring the clearance between live-line work combinations, targeting UHV/EHV AC transmission lines. By extracting the contour information of classified laser point cloud data, the proposed method can efficiently calculate the clearance distance for a given spatial point, reducing the distance calculation errors caused by sampling errors in the original laser point cloud data. It can also significantly improve the efficiency of distance detection. The research conducted experiments on the 500 kV AC transmission line of the UHV Line in Henan Province, demonstrating a significant improvement in the accuracy and efficiency of the proposed method compared to directly computing based on point clouds.