A data sending method, comprising: receiving, by a first terminal device, first information from a network device; and determining, by the first terminal device, at least two carriers based on the first information, wherein the at least two carriers are used to transmit at least two pieces of data corresponding to a same transport block, and the at least two carriers are in a one-to-one correspondence with the at least two pieces of data, wherein the first information is used to indicate the at least two carriers, and the first information is used to indicate that the at least two pieces of data corresponding to the same transport block are transmitted on the at least two carriers; and sending, by the first terminal device, the at least two pieces of data to a second terminal device or the network device by using the at least two carriers; characterized in that the first information comprises at least two pieces of first identification information, and the at least two pieces of first identification information are used to indicate the at least two carriers; wherein the first identification information includes a carrier indicator field, CIF, wherein the receiving and the determining comprises: the first terminal receiving a plurality of pieces of first information from the network device, each piece of first information includes a CIF of another carrier in addition to a CIF of a carrier used by the first information; and the first terminal determining the at least two carriers based on CIFs included in each piece of first information; or wherein the first information comprises at least two pieces of indication information, any one of the at least two pieces of indication information comprises one piece of first identification information and one piece of second identification information, the one piece of first identification information is used to indicate one of the at least two carriers, second identification information in the at least two pieces of indication information is the same, and the second identification information in the at least two pieces of indication information is used to indicate that the at least two pieces of data corresponding to the same transport block are transmitted on the at least two carriers. receiving, by a first terminal device, first information from a network device; and determining, by the first terminal device, at least two carriers based on the first information, wherein the at least two carriers are used to transmit at least two pieces of data corresponding to a same transport block, and the at least two carriers are in a one-to-one correspondence with the at least two pieces of data, wherein the first information is used to indicate the at least two carriers, and the first information is used to indicate that the at least two pieces of data corresponding to the same transport block are transmitted on the at least two carriers; and sending, by the first terminal device, the at least two pieces of data to a second terminal device or the network device by using the at least two carriers; characterized in that the first information comprises at least two pieces of first identification information, and the at least two pieces of first identification information are used to indicate the at least two carriers; wherein the first identification information includes a carrier indicator field, CIF, wherein the receiving and the determining comprises: the first terminal receiving a plurality of pieces of first information from the network device, each piece of first information includes a CIF of another carrier in addition to a CIF of a carrier used by the first information; and the first terminal determining the at least two carriers based on CIFs included in each piece of first information; or wherein the first information comprises at least two pieces of indication information, any one of the at least two pieces of indication information comprises one piece of first identification information and one piece of second identification information, the one piece of first identification information is used to indicate one of the at least two carriers, second identification information in the at least two pieces of indication information is the same, and the second identification information in the at least two pieces of indication information is used to indicate that the at least two pieces of data corresponding to the same transport block are transmitted on the at least two carriers.