A data transmission method, comprising: determining, by an access network device, a transmission mode of service data, wherein the transmission mode comprises a one-time transmission mode and an automatic repeat transmission mode; sending, by the access network device, first indication information to a terminal device, wherein the first indication information indicates the determined transmission mode; and sending, by the access network device, the service data to the terminal device using the determined transmission mode, wherein the sending, by the access network device, the service data to the terminal device using the determined transmission mode comprises: when the determined transmission mode is the automatic repeat transmission mode, sending, by the access network device, at least one first coded data block to the terminal device; receiving, by the access network device, acknowledgement information or negative acknowledgement information corresponding to the at least one first coded data block from the terminal device; and if the access network device receives the negative acknowledgement information, sending, by the access network device, at least one second coded data block to the terminal device, the method being characterized by: when the determined transmission mode is the one-time transmission mode, sending, by the access network device, M coded data blocks to the terminal device, wherein M ≥ 2; the M coded data blocks are coded data blocks that can be separately decoded, and the M coded data blocks carry same service data, and the M coded data blocks comprise the at least one first coded data block and the at least one second coded data block, wherein that the M coded data blocks are coded data blocks that can be separately decoded means that each of the M coded data blocks can be separately decoded, and further at least two of the M coded data blocks can be jointly decoded. determining, by an access network device, a transmission mode of service data, wherein the transmission mode comprises a one-time transmission mode and an automatic repeat transmission mode; sending, by the access network device, first indication information to a terminal device, wherein the first indication information indicates the determined transmission mode; and sending, by the access network device, the service data to the terminal device using the determined transmission mode, wherein the sending, by the access network device, the service data to the terminal device using the determined transmission mode comprises: when the determined transmission mode is the automatic repeat transmission mode, sending, by the access network device, at least one first coded data block to the terminal device; receiving, by the access network device, acknowledgement information or negative acknowledgement information corresponding to the at least one first coded data block from the terminal device; and if the access network device receives the negative acknowledgement information, sending, by the access network device, at least one second coded data block to the terminal device, the method being characterized by: when the determined transmission mode is the one-time transmission mode, sending, by the access network device, M coded data blocks to the terminal device, wherein M ≥ 2; the M coded data blocks are coded data blocks that can be separately decoded, and the M coded data blocks carry same service data, and the M coded data blocks comprise the at least one first coded data block and the at least one second coded data block, wherein that the M coded data blocks are coded data blocks that can be separately decoded means that each of the M coded data blocks can be separately decoded, and further at least two of the M coded data blocks can be jointly decoded. when the determined transmission mode is the automatic repeat transmission mode, sending, by the access network device, at least one first coded data block to the terminal device; receiving, by the access network device, acknowledgement information or negative acknowledgement information corresponding to the at least one first coded data block from the terminal device; and if the access network device receives the negative acknowledgement information, sending, by the access network device, at least one second coded data block to the terminal device, the method being characterized by: when the determined transmission mode is the one-time transmission mode, sending, by the access network device, M coded data blocks to the terminal device, wherein M ≥ 2; the M coded data blocks are coded data blocks that can be separately decoded, and the M coded data blocks carry same service data, and the M coded data blocks comprise the at least one first coded data block and the at least one second coded data block, wherein that the M coded data blocks are coded data blocks that can be separately decoded means that each of the M coded data blocks can be separately decoded, and further at least two of the M coded data blocks can be jointly decoded.