Abstract: A novel fast algorithm for searching the transmission section based on partition of power grid is presented in this paper, which partitions power grid by applying GN algorithm in complex grid community detection, and searches transmission section by combing related knowledge of path matrix in graph theory. At the same time, such comprehensive indexes as key betweenness are used to search vulnerable lines and the heavy load lines as interval contact lines when partitioning grid. Therefore, previous problems caused by not considering grid topological structure and line load in the traditional network partition are effectively solved, which can overcome the leaking select problems brought by not be chosen in grid area greatly. Simulation results of IEEE 39-bus system show that the proposed algorithm is feasible and available.