This application relates to the field of wireless communication, and in particular, to a multi-channel hybrid transmission technology. In an embodiment, a data transmission method comprises: generating, by a first wireless communications device, a physical protocol data unit (PPDU), wherein the PPDU comprises a legacy short training field (L-STF), a legacy long training field (L-LTF), a legacy signal field (L-SIG), and two signature symbols after the L-SIG in a time-domain, and wherein the two signature symbols are identical and are modulated based on binary phase shift keying (BPSK), the two signature symbols identify a wireless communications standard the PPDU complies with; and transmitting, by the first wireless communications device, the PPDU to a second wireless communications device.