This paper takes the multi-regional interconnected power system as the research object, and studies the detection and defense of multi-region interconnected power system under hybrid attack. Firstly, a mathematical model of multi-regional interconnected power system is established, the location and type of network attacks suffered by multi-regional interconnected power system are analyzed, and false data injection attacks and denial of service attack models are established. Secondly, diagnose denial of service attacks based on whether packets are received, and the recently received packet compensates for the lost packet, the defense of denial-of-service attack is realized. Then, based on the cubature Kalman filter algorithm, false data injection attacks are detected, and exponential smoothing is used to defend against false data injection attacks. Finally, taking the two-region interconnected power system as an example, the simulation experiment shows that the designed control algorithm can effectively overcome the adverse effects of hybrid attacks on the system, and realize the power balance and frequency stability of the power system.