The invention provides a method for evaluating the forest fire spreading risk of a power transmission channel. The method for evaluating the forest fire spreading risk of the power transmission channel is characterized by comprising the following steps that S101, a remote sensing image is preprocessed; S102, fire points and obstruction objective image elements are extracted based on the corrected remote sensing image; S103, fire outbreak point calculation is carried out; S104, the forest fire spreading speed is calculated; S105, burning range estimation is performed within predefined time duration; S106, a power transmission tower set affected by a fire is searched; S107, the forest fire spreading risk of the power transmission channel is evaluated. By the adoption of the method, various data of the wind speed and direction, the topographic slope, the vegetation type, ground barriers and the like are collected, so that a calculation method including forest fire spreading conditions and relevant factors for causing power transmission line tripping by the fire is established, hence, evaluating calculation of the forest fire spreading risk of the power transmission channel is achieved, and the national economy loss caused by large-area outage of a power grid can be effectively prevented and reduced.