The invention discloses an evaluation method for evaluating the branch importance of a power system. The comprehensive importance index of a to-be-evaluated branch is obtained, and then the branch importance of the power system is evaluated. Tl* represents an active power transmission betweenness of the to-be-evaluated branch after being normalized. img file = 'DDA 0001143047330000012. TIF 'wi = '51 'he = '57' represents the impact resistance index of the to-be-evaluated branch after being normalized. Sigma represents the weight coefficient of the active power transmission betweenness. Mu represents the weight coefficient of the impact resistance index. According to the technical scheme of the invention, the complicated network theory and the entropy theory are organically combined, and the branch importance is comprehensively evaluated in the two aspects of the active transmission betweenness and the impact resistance index. A configured branch comprehensive importance index gives consideration to both the branch structure and the state importance. In this way, not only the contribution degree and the carrying capacity of an important branch during the power transfer process can be reflected, but also the influence of the on-off impact of the branch on the system is also considered. Therefore, the method is more accurate and more reasonable. The consideration range is more comprehensive and the evaluation result is more close to the real situation of the power grid.