A probability evaluation method of failure caused by typhoon to a power transmission line is suitable for evaluating failure probability after the power transmission line is affected by the typhoon. The method mainly comprises the steps of quantitative evaluation on the power transmission line affected by the typhoon as well as environmental factors and probability modeling of the line failure caused by the typhoon. In the quantitative evaluation, ways of the failure caused by the typhoon to the power transmission line and key factors including inner factors (design strength, state and the like of lines) and outer factors (typhoon, terrain, rainfall and other factors) are mainly evaluated; and in the probability modeling, a reasonable failure probability model is mainly established to calculate the line failure probability corresponding to the quantitative evaluation results of the key factors. The probability evaluation method has the beneficial effects that the evaluation on various loads and real-time anti-wind capability of complicated lines and towers is avoided, the effect of the inner factors and the outer factors and the characteristics of the various failure ways are simultaneously considered, a mechanism that the failure of the line is caused by the typhoon is satisfied, and the capacity of a power system in defending the typhoon disaster is improved in combination with a wide-area measurement, analysis, protection and control system.