A terminal device can modify, through an RRC link providing a normal service, an RRC link in which an RLF or channel quality deterioration occurs, so that the terminal device maintains RRC links to at least two network devices, thereby ensuring RRC reliability while the failed RRC link or the RRC link whose channel quality is poor is replaced in time. The method includes: sending, by a terminal device, a first link modification request to a first network device through a first RRC link; receiving, by the terminal device, an RRC link modification message and a transmission parameter that are sent by the first network device through the first RRC link; and setting up, by the terminal device, a target RRC link to a target network device based on the transmission parameter, and maintaining both the target RRC link and the first RRC link.