Embodiments of this application disclose a data transmission method and a communications apparatus. A method in an embodiment includes: sending, by a network device, first data to a terminal in a first subframe through a first channel, where the first channel is a channel occupied in a channel system by a service between the network device and the terminal; performing, by the network device, channel listening on a channel that is not occupied in the channel system by the service; and when there is a second channel in an idle state, sending, by the network device, second data of the service to the terminal in a second subframe through the first channel and the second channel, where the second subframe is after the first subframe. The service includes the first data and the second data, and a data frame of the service includes the first subframe and the second subframe.