The invention relates to a windage yaw flashover risk assessment method in a sand and dust environment of a power transmission line. The method comprises the following steps: S1, identifying a windageyaw flashover risk source; S2, establishing a power transmission line windage yaw flashover risk assessment index system, and performing risk grading; S3, giving a risk assessment scoring standard according to the accident case and the statistical data, and calculating a general standard weight; S4, calculating a specific power transmission line standard weight; S5, evaluating the influence of sand and dust factors on the air insulation strength; S6, updating weight factor changes; and S7, evaluating the real-time windage yaw flashover risk of the specific power transmission line. According to the method, the influence of sand and dust on windage yaw flashover of the power transmission line is fully considered. Meanwhile, the weight value of the evaluation index is updated in real time through feedback data in the windage yaw flashover accident development process, and the risk situation of windage yaw flashover of the power transmission line in the sand and dust environment can be judged more reasonably.