An Ethernet Switch Ring (ESR) protection method for introducing the pre-up state for the transit node, includes, after a loop failure is recovered, the transit node on the loop entering the pre-up state if not receiving the loop failure protocol message within a set time. And when the transit node is in the pre-up state and the loop fails again, i.e., the transit node receives the loop failure protocol message in the pre-up state, the transit node opens the master and slave ports and refreshes the MAC address. Effectively, the transit node is an ESR transit node.