The method of power transformers full life cycle economic-physical comprehensive life evaluation is presented to solve the problem of quantitative life prediction. First, the life cycle cost model of power transformer is set up. The relationship between the components of the life cycle cost and the running time is analyzed. The economic life of power transformer is obtained by using the minimum full life cycle cost principle. The physical life evaluation system of power transformer is built from three aspects:the degree of main insulation aging, the state of insulation operation and the risk of component defects. The weight of each evaluation index is given by analytic hierarchy process, and then the physical life of power transformer is calculated. Considering the economic life, the economic-physical comprehensive life calculation method of power transformer is put forward based on the power transformer physical life. Finally, a power transformer is taken as an example to calculate the comprehensive economic-physical life, and the rationality and practicability of the method are verified. This work is supported by National Natural Science Foundation of China (No. 51777199).