Communication system and method and device for detecting redundancy failure of communication system

The invention discloses a method for detecting redundancy failure of a communication system, which comprises the following steps of: when a first redundancy device serving as a sender identity and a receiving device are in a safe state communication process, when a data packet transmitted by a second redundancy device serving as a redundancy sending identity is received, determining a current data packet as an initial data packet, triggering a guard time timer for judging whether the current redundancy switching operation fails to start; if a new data packet transmitted by the device with the sender identity is received within the preset security state guard time, it is determined that a redundant fault occurs, and the new data packet is utilized to update the current initial data packet, so that the data packets continuously received after the current initial data packet are determined to be in a non-security state, the security state guard time comprises a preset number of data packet sending time intervals