In recent years, there have been more and more power grid accidents caused by environmental changes in transmission lines, which have seriously affected the safety and stability of power grids. Considering that the influencing factors of the transmission line mountain fire risk are many and complicated, the mountain fire risk assessment model of the transmission line channel is proposed. According to the statistical analysis of meteorological data, the probability of occurrence of hill fire under different fire danger meteorological grades is determined, combined with the air gap when the mountain fire occurs. The probability calculation model of the breakdown is established, and the risk assessment of the model transmission channel under the mountain fire condition with temporal and spatial distribution characteristics is established. The validity of the model is verified by an example. The experimental results show that the model can effectively predict the fire risk of the transmission channel. The research work has provided reference and reference for the intelligent risk control of transmission channels in China.