A data transmission method, wherein the method comprises: sending, by a first device, first information by using a first carrier, wherein the first information is used to indicate that the first device uses N carriers in M carriers to send data, wherein N is an integer greater than or equal to 2, and N is less than or equal to M; and sending, by the first device, the data by using the N carriers; wherein the first information is specifically used to indicate whether each carrier other than the first carrier in the M carriers comprises a first time-frequency resource, wherein the first time-frequency resource is a time-frequency resource used when the first device sends the data; wherein the first information comprises M-1 bits, the M-1 bits are in a one-to-one correspondence to M-1 carriers, and each bit is used to indicate whether a corresponding carrier comprises the first time-frequency resource, wherein the M-1 carriers are carriers other than the first carrier in the M carriers, and before the sending of the first information, the method further comprises: determining, by the first device, any one of the M carriers as the first carrier, wherein the first carrier carries a first identifier sent by the first device, wherein the first identifier is preconfigured, or is configured by a network device, and the first identifier is used to indicate that the carrier that carries the first identifier carries the first information, or wherein the first carrier carries a synchronization signal, and a carrier other than the first carrier in the M carriers does not carry the synchronization signal, or wherein a synchronization signal carried in the first carrier corresponds to a first sequence, wherein the first sequence is a preconfigured sequence, or the first sequence is a sequence configured by a network device, and the first sequence is used to indicate that the carrier that carries the synchronization signal corresponding to the first sequence carries the first information. sending, by a first device, first information by using a first carrier, wherein the first information is used to indicate that the first device uses N carriers in M carriers to send data, wherein N is an integer greater than or equal to 2, and N is less than or equal to M; and sending, by the first device, the data by using the N carriers; wherein the first information is specifically used to indicate whether each carrier other than the first carrier in the M carriers comprises a first time-frequency resource, wherein the first time-frequency resource is a time-frequency resource used when the first device sends the data; wherein the first information comprises M-1 bits, the M-1 bits are in a one-to-one correspondence to M-1 carriers, and each bit is used to indicate whether a corresponding carrier comprises the first time-frequency resource, wherein the M-1 carriers are carriers other than the first carrier in the M carriers, and before the sending of the first information, the method further comprises: determining, by the first device, any one of the M carriers as the first carrier, wherein the first carrier carries a first identifier sent by the first device, wherein the first identifier is preconfigured, or is configured by a network device, and the first identifier is used to indicate that the carrier that carries the first identifier carries the first information, or wherein the first carrier carries a synchronization signal, and a carrier other than the first carrier in the M carriers does not carry the synchronization signal, or wherein a synchronization signal carried in the first carrier corresponds to a first sequence, wherein the first sequence is a preconfigured sequence, or the first sequence is a sequence configured by a network device, and the first sequence is used to indicate that the carrier that carries the synchronization signal corresponding to the first sequence carries the first information.