With the continuously expanding scale of the electric power grid in recent years, wildfire has been one of the main disasters which threaten the security of operation of power grid. Therefore, accurate, reliable, professional wildfire rating and forecasting along transmission lines has become a big challenge for entrepreneurs in power grid. In this paper, the combination of factors in power grid and environmental factors to cause wildfire was discussed firstly, and a wildfire rating and forecasting indicator system was established. Then a wildfire rating and forecasting model and a five-grade rating standard were built. Finally, according to the actual situation in a northern province in China, 8 data sets were used to test the method. The prediction result is largely identical to the actual situation of power grid operation, and shows that this method is more professional and more valid compared with other methods.