An information transmission method and a device are provided. The information transmission method includes: receiving, by a terminal device, downlink control information sent by a network device, the downlink control information including a resource allocation field, the resource allocation field being used to indicate allocated resource block(s) or a subcarrier resource. The method further includes determining, by the terminal device, an allocated resource based on the downlink control information, and sending information on the allocated resource. According to the method and the device provided in embodiments of this application, a coverage capability of a network is improved, and the method and the device may be applied to the internet of things, for example, MTC, IoT, LTE-M, and M2M.