The invention discloses a method and a device for protecting a ring network. The method comprises the following steps that: nodes on the ring network detect whether the link states of the nodes and adjacent nodes are changed or not through a fault detection message of a link layer; when the link states are changed, the nodes on the ring network are determined to be fault upstream adjacent nodes; and the nodes on the ring network switch the service traffic from a working tunnel to a protection tunnel, wherein the protection tunnel performs ring dismounting processing of the service traffic on service ring-out nodes. By adopting the method and the device, the safety and stability of a system are improved.