Against the lack of a redundancy method to ensure the smart substations’ high availability of the communication based on multi-mode fiber, this paper presents a ring network redundancy method, which is based on the response mechanism to improve communication availability. This method achieves the redundancy protection by the ring network equipments’ determining the response and setting the port status, controls the amount of CPU port’s data by constructing data frames that can be identified and processed by switch chip as test frames, and shortens the redundant recovery time by the rational allocation and effective utilization of the CPU. The method is applied to the simulation tests in the smart substation system using the ring network equipments of the laboratory. Tests show the redundancy recovery time is less than 30 ms. Compared with MRP protocol, the load of the device itself is reduced about 10% when running this method. This method ensures the real-time and reliability of communication based on multimode optical network in the smart substations.