A data transmission method, comprising: receiving, by a receiving circuit in a media access controller, MAC, N packets, wherein the N packets sequentially arrive at the MAC in a time sequence from the first packet to the N th packet, and N is a positive integer greater than 1; generating, by a distributing circuit in the MAC, a first data block and a second data block, wherein the first data block comprises a first set, the first set comprises the first packet to the M th packet, and the first packet to the M th packet are sequentially carried in the first data block in a location sequence from the first packet to the M th packet; the second data block comprises a second set, the second set comprises the (M+1) th packet to the N th packet, and the (M+1) th packet to the N th packet are sequentially carried in the second data block in a location sequence from the (M+1) th packet to the N th packet; the first data block comprises a first identifier, the second data block comprises a second identifier, the first identifier is used to indicate a time sequence that the first set arrives at the MAC, the second identifier is used to indicate a time sequence that the second set arrives at the MAC, M is a positive integer, and M is less than N; distributing, by the distributing circuit, the first data block to a first circuit in the MAC, and distributing, by the distributing circuit, the second data block to a second circuit in the MAC; converting, by the first circuit, the first data block into first data, and converting, by the second circuit, the second data block into second data; and sending, by the first circuit, the first data through a first channel, and sending, by the second circuit, the second data through a second channel, wherein the first channel and the second channel are implemented by using different optical transport network timeslots, different synchronous digital hierarchy timeslots, different wavelengths, or different optical fibers. receiving, by a receiving circuit in a media access controller, MAC, N packets, wherein the N packets sequentially arrive at the MAC in a time sequence from the first packet to the N th packet, and N is a positive integer greater than 1; generating, by a distributing circuit in the MAC, a first data block and a second data block, wherein the first data block comprises a first set, the first set comprises the first packet to the M th packet, and the first packet to the M th packet are sequentially carried in the first data block in a location sequence from the first packet to the M th packet; the second data block comprises a second set, the second set comprises the (M+1) th packet to the N th packet, and the (M+1) th packet to the N th packet are sequentially carried in the second data block in a location sequence from the (M+1) th packet to the N th packet; the first data block comprises a first identifier, the second data block comprises a second identifier, the first identifier is used to indicate a time sequence that the first set arrives at the MAC, the second identifier is used to indicate a time sequence that the second set arrives at the MAC, M is a positive integer, and M is less than N; distributing, by the distributing circuit, the first data block to a first circuit in the MAC, and distributing, by the distributing circuit, the second data block to a second circuit in the MAC; converting, by the first circuit, the first data block into first data, and converting, by the second circuit, the second data block into second data; and sending, by the first circuit, the first data through a first channel, and sending, by the second circuit, the second data through a second channel, wherein the first channel and the second channel are implemented by using different optical transport network timeslots, different synchronous digital hierarchy timeslots, different wavelengths, or different optical fibers.