A data transmission method and an apparatus are disclosed. The method includes: generating, by a first transmit device, a data frame sequence, where the first data frame sequence includes a first data frame, the first data frame includes a switching interval, the switching interval includes first identification information, and the first data frame corresponds to a first data period; detecting, by the first transmit device, whether a beam adjustment request is received within the first data period, and if the beam adjustment request is received, setting the first identification information in the switching interval of the first data frame to invalid; or if no beam adjustment request is received, setting the first identification information to valid; and sending, by the first transmit device, the first data frame.