The icing of high voltage transmission lines is one of the key disaster factors for the safe operation, management and maintenance department of a power grid, and icing thickness is the key index of risk assessment and deicing strategy. In view of the low accuracy and efficiency of the existing ice thickness extraction methods, a laser point cloud inversion method for ice thickness is proposed. First, the three-dimensional spatial model of the transmission line is extracted from a two-stage laser point cloud, and the horizontal stress of the no-load transmission line is extracted by combining the line parameters. Secondly, the horizontal stress of the ice-covered line is calculated according to the state equation. Finally, a three-dimensional spatial model and the horizontal stress of the ice-covered transmission line are integrated, and the comprehensive specific load is calculated, so as to realize fast inversion of the average ice thickness. Experimental results show that this method can quickly realize the inversion of the ice thickness. The maximum inversion error of ice thickness is 0.30 mm, and the relative error is 6.58%. The research has important application value for ice risk monitoring and evaluation of high-voltage transmission lines. This work is supported by the National Key Research and Development Program of China (No. 2018YFE0184300) and the National Natural Science Foundation of China (No. 41961060 and No. 41271230).