A method for protecting service reliability, wherein the method is applied to a network virtualization system based on control and forwarding separation, the network virtualization system comprises master nodes and slave nodes, a slave node of the slave nodes is controlled by a pair of mutually main-backup master nodes, the master nodes be provided with a control function and a forwarding function, while the slave node has the forwarding function, the pair of mutually main-backup master nodes comprise a main master node and a backup master node, a first virtual link is arranged between the slave node and the main master node controlling the slave node, a second virtual link is arranged between the slave node and the backup master node controlling the slave node, and the method comprises: receiving, by the slave node, service type information sent by one of the master nodes controlling the slave node through a control channel between said master node controlling the slave node and the slave node, wherein the service type information comprises L2VPN and L3VPN, the control channels are arranged between the main master node controlling the slave node and the slave node and between the backup master node controlling the slave node and the slave node; determining, by the slave node, a main virtual link and a backup virtual link according to the service type information; wherein the main virtual link is a virtual link of the first virtual link and the second virtual link, the main virtual link is a virtual link used for transmitting a service data message, the backup virtual link is the other virtual link rather than the main virtual link of the first virtual link and the second virtual link; detecting, by the slave node, whether the main virtual link and the backup virtual link have failure; and when detecting that the main virtual link has failure and the backup virtual link has no failure, switching, by the slave node, to transmit the service data message from the main virtual link to the backup virtual link; when the service type is L3VPN, determining, by the slave node, the main virtual link and the backup virtual link according to interface routing state information respectively sent by the main master node controlling the slave node and the backup master node controlling the slave node, wherein the interface routing state information refers to routing state information of a virtual remote logical interface having a corresponding relationship with an external interface of the slave node and located on the main master node or the backup master node, and the external interface refers to an interface of the slave node, which is connected with a network device outside the network virtualization system based on control and forwarding separation. receiving, by the slave node, service type information sent by one of the master nodes controlling the slave node through a control channel between said master node controlling the slave node and the slave node, wherein the service type information comprises L2VPN and L3VPN, the control channels are arranged between the main master node controlling the slave node and the slave node and between the backup master node controlling the slave node and the slave node; determining, by the slave node, a main virtual link and a backup virtual link according to the service type information; wherein the main virtual link is a virtual link of the first virtual link and the second virtual link, the main virtual link is a virtual link used for transmitting a service data message, the backup virtual link is the other virtual link rather than the main virtual link of the first virtual link and the second virtual link; detecting, by the slave node, whether the main virtual link and the backup virtual link have failure; and when detecting that the main virtual link has failure and the backup virtual link has no failure, switching, by the slave node, to transmit the service data message from the main virtual link to the backup virtual link; when the service type is L3VPN, determining, by the slave node, the main virtual link and the backup virtual link according to interface routing state information respectively sent by the main master node controlling the slave node and the backup master node controlling the slave node, wherein the interface routing state information refers to routing state information of a virtual remote logical interface having a corresponding relationship with an external interface of the slave node and located on the main master node or the backup master node, and the external interface refers to an interface of the slave node, which is connected with a network device outside the network virtualization system based on control and forwarding separation.