A method for link switching, characterized by comprising: establishing, by a first communication device, a second link between the first communication device and a second communication device in a case that service transmission cannot be performed by using a first link between the first communication device and the second communication device; and performing, by the first communication device, the service transmission by using the second link, wherein communication devices on the first link and communication devices on the second link are different; wherein the first communication device is a terminal device and the second communication device is a network device, the first link is a relay link and the communication devices on the first link comprise the first communication device, the second communication device and a relay device, and the second link is a second access link and the communication devices on the second link comprise the first communication device and the second communication device; wherein the method further comprises: notifying, by the first communication device, the network device to delete the relay link in a case that the first communication device performs the service transmission by using the second link; wherein establishing, by a first communication device, a second link between the first communication device and a second communication device in a case that service transmission cannot be performed by using a first link between the first communication device and the second communication device comprises: sending, by the first communication device, a Non-Access Stratum, NAS, message to a Core Network, CN, wherein the NAS message comprises a service request or a Protocol Data Unit, PDU, session establishment request. establishing, by a first communication device, a second link between the first communication device and a second communication device in a case that service transmission cannot be performed by using a first link between the first communication device and the second communication device; and performing, by the first communication device, the service transmission by using the second link, wherein communication devices on the first link and communication devices on the second link are different; wherein the first communication device is a terminal device and the second communication device is a network device, the first link is a relay link and the communication devices on the first link comprise the first communication device, the second communication device and a relay device, and the second link is a second access link and the communication devices on the second link comprise the first communication device and the second communication device; wherein the method further comprises: notifying, by the first communication device, the network device to delete the relay link in a case that the first communication device performs the service transmission by using the second link; wherein establishing, by a first communication device, a second link between the first communication device and a second communication device in a case that service transmission cannot be performed by using a first link between the first communication device and the second communication device comprises: sending, by the first communication device, a Non-Access Stratum, NAS, message to a Core Network, CN, wherein the NAS message comprises a service request or a Protocol Data Unit, PDU, session establishment request.