Implementing the identification and control of transmission sections is of great significance for the prevention of chain trip accidents in a power system and the safe and reliable operation of the entire system. A method for identifying transmission sections based on an AP clustering algorithm is proposed. The Euclidean distance of each node is selected, i.e. the geographical division of the power network is realized to identify the initial transmission sections. On this basis, combined with the line outage distribution factor of each line in the network, fragile lines are included in the line composition of the transmission sections, and the final transmission sections are identified. Aiming at the control of the transmission sections, an active power safety correction method for the transmission sections is proposed. The non-linear programming model is calculated by the primal-dual interior point method, and the power flow reconstruction of the power network is implemented to eliminate the active overload of the internal lines of the sections. The transmission sections of the IEEE 14-node and 39-node networks are identified, and the analysis and verification of the safety correction of active power flow on the IEEE 39-node and 118-node networks are performed. The results show the feasibility and effectiveness of the proposed method. This work is supported by the Science and Technology Project of State Grid Corporation of China “Study and Application of Large Power Grid Pre-Dispatch Key Technology” (No. SGZJ0000KXJS1800285).