As to power oscillation phenomenon of the interconnected power systems can be further revealed, mode energy flow function is proposed. Then network mode energy is calculated, and the power oscillation of interconnected power grid is analyzed by oscillation energy. Thus, mode shape index based on the wide-area measurement information is constructed to judge power oscillation generator groups. At the same time, the main oscillation path index of power system is set up to identify main oscillation path, and in order to get the energy interaction main oscillation path. Through simulation of four machine two area and 8-machine 36 node examples, the effectiveness of proposed power oscillation energy analysis and the main oscillation path identification method is validated. This work is supported by National Natural Science Foundation of China (No. 51377017).