The invention discloses a reverse communication method of a crossing safety zone, a device and a system. The method includes sending explore packets to file gateways of isolation devices, obtaining working state information of the isolation devices through echo packets of the explore packets, comparing the working state information of the isolation devices, and choosing one corresponding gateway of one of the isolation devices to transmit a reverse communication packet according to comparison results. By means of the method, the device and the system, a communication bus crossing a safety zone can be set up, and the structure of a network can be simplified. One of working states of the isolation devices is chosen, the communication packets are coordinated for transmission, and the resource utilization rate of equipment is improved. Exchange visits of systems are benefited, and therefore system performance, expansibility and reliability are improved.