Evaluation on energy characteristics of a wind-excited transmission tower-line system is actively carried out in this study. The analytical method of a transmission tower-line system is established. The evaluation criteria of energy responses is developed and applied to the wind response analysis of a transmission tower. A real transmission tower-line system constructed in China is taken as an example to examine the feasibility and reliability of the proposed approach. The observations from numerical investigation indicate that the proposed energy evaluation criteria can be effectively utilized in the examination on structural dynamic performance.