In order to improve the reliability of network communication in the power grid dispatching automation system， a hot-standby redundancy mechanism based on dual network interface card（NIC） is proposed. The mechanism consists of fault detection， fault switching and fault recovery. Fault detection information is acquired by sending probe packets to the core network devices. Fault switching program switches IP address when devices are broken down. IP address is switched back when device failure is restored. The hot-standby redundancy mechanism has the characteristics of easy implementation， simple deploying， better generalization and high reliability. The mechanism is adopted in the power grid dispatching automation system.