A method of power system preventive control candidate measures identification self-adaptive to external environment, which is applicable to dynamic identification of stations and power equipment under the effect of calamity, and judgment of preventive control measures that lose or restore control capability, and those for which control range or cost has changed. Automatic online identification of set of preventive control candidate measures includes two tasks: identification of stations and power equipment under the effect of calamity, and adjustment of the space of preventive control measures. According to information of power transmission line fault probability due to calamity, online dynamic quantitative assessment of stations and equipment is performed under the effect of external environment, and automatically correct control range and control cost of the measures according to the effect on equipment, so that the result of preventive control adapts to real-time external environment, ensuring feasibility and economy of auxiliary decision making.