A data transmission method is provided to resolve a problem of data transmission delay in a DRX mechanism. A RAN device sends, to a terminal in a DRX active period, first grant information that is used to perform initial transmission grant for first data. The RAN device sends, to the terminal in a retransmission active time in which the terminal expects to receive a retransmission grant for the first data, second grant information that is used to perform initial transmission grant for second data. Then the RAN device and the terminal remain in an active state in an activation extension time that is after sending of the second grant information.