Abstract: This application provides a data transmission method and a device. The method includes: obtaining, by a transmit end device, a modulation symbol sequence in multiple time-frequency resource element groups, wherein a size of the time-frequency resource element group is agreed on in a protocol, or determined based on a transmission parameter; performing, by the transmit end device, interleaving processing on the modulation symbol sequence using the time-frequency resource element group as an interleaving unit, to obtain an order in which the modulation symbol sequence is mapped onto the multiple time-frequency resource element groups, wherein multiple consecutive modulation symbol groups in the modulation symbol sequence are mapped onto at least two of the multiple time-frequency resource element groups; and sending, by the transmit end device, the modulation symbol sequence in the order in which the modulation symbol sequence is mapped onto the multiple time-frequency resource element groups.