A data transmission method and a related product are provided. The method includes: when a HARQ buffer is not empty, a user equipment selects a grant used for previous data transmission to transmit data that needs to be retransmitted; or, when the HARQ buffer is empty, the user equipment selects one current grant of Semi-Persistent scheduling to transmit new data or selects multiple current grants of Semi-Persistent scheduling to transmit new data according to a carrier access manner allowed by the user equipment.