Abstract: Aiming at the problem of low accuracy and low efficiency of traditional manual measurement methods of transmission line, a combined laser radar system in which airborne LiDAR system works collaboratively with terrestrial laser scanner is proposed to measure the transmission line. The airborne LiDAR system is responsible for the acquisition of point cloud data in the transmission line corridor and the terrestrial laser scanner is responsible for the acquisition of high precision point cloud data of the electric tower. By calculating the rotation matrix and translation vector between the two coordinate systems, two sets of point clouds can be merged. The application test is carried out in Zhangbei 500 kV high-voltage transmission line project, the experimental results show that the system could effectively and accurately detect the dangerous points in the transmission line corridor and monitor the inclination and deformation of the electric tower, which has a certain practical value.