This application provides a signal transmission method and apparatus. The method is applied to a communications system including at least three nodes, a second node in the at least three nodes communicates with a third node by using a first node, and the method includes: determining, by the first node, a status of a link between the first node and the second node; and sending, by the first node, first notification information to the third node when determining that the link between the first node and the second node is abnormal, where the first notification information is used to indicate that the link between the first node and the second node is abnormal.