This application provides an information transmission method and a device, and relates to the field of wireless communications technologies, to resolve a prior-art problem that a requirement of a future network cannot be met because only single-hop relay (RN) network access is supported. In the method, a first device receives a first message that is sent by a base station, where the first message includes first indication information and system information, and the first indication information is used to determine whether to broadcast the system information; and the first device determines, according to the first indication information, that the system information needs to be broadcast, and broadcasts the system information. In this application, the first message of the base station carries the first indication information. In this way, after receiving the first message, the first device may determine to broadcast the system information according to the first indication information, so that a target device receiving the system information accesses the base station by using the system information. This implements multi-hop relay networking, and the method provided in this application may be applied to establishment of a multi-hop relay network.