Ethernet communication method and Ethernet communication device

The invention discloses an Ethernet communication method and an Ethernet communication device which aim to simplify Ethernet communication. The method includes: setting a network terminal as a master unit, setting another network terminal as a spare terminal, and setting the rest network terminals as slave terminals; keeping the master unit to be connected with the spare terminal; and when the master unit communicates with one slave terminal, enabling the spare terminal to be disconnected with a network. The device is characterized in that a transmission line and a receiving line of the master unit are connected with the network, the spare terminal and receiving lines of the slave terminals are connected with the network, the transmission line is connected with the network via a controlled switch, a control line is connected among the controlled switch of the spare terminal, the slave terminals and controlled switches connected with the slave terminals, and reverse isolation diodes are serially connected onto the control line. Compared with the prior art, the method and the device have the advantages that connected communication of the master unit with the spare terminal or with one slave terminal is guaranteed, the network structure of the Ethernet is simplified, and cost of network equipment is reduced.