A duplicate transmission configuration method for ensuring reliability through redundant transmission according to 5G standards, wherein the method comprises: when a master access network device determines that a transmission mode of a split bearer is duplicate transmission, configuring (1001, 1101), by the master access network device, a radio link control, RLC, entity of the split bearer in the master access network device to an unacknowledged mode, UM, wherein RLC entities of the split bearer are located in the master access network device, a secondary access network device, and a terminal device separately; transmitting (1002, 1102), by the master access network device, indication information to the secondary access network device, wherein the indication information is used to indicate that a transmission mode of the split bearer is duplicate transmission, and the indication information is used to configure the RLC entity of the split bearer in the secondary access network device to the UM; and transmitting (1004, 1104), by the master access network device, the indication information to the terminal device, wherein the indication information is used for the terminal device to perform duplicate transmission, wherein the method further comprises: receiving, by the master access network device, first configuration information from the secondary access network device, wherein the first configuration information indicates that a mode of the RLC entity of the split bearer in the secondary access network device is the UM; and transmitting, by the master access network device, the first configuration information and second configuration information to the terminal device, wherein the second configuration information indicates that a mode of the RLC entity of the split bearer in the master access network device is the UM, and the first configuration information and the second configuration information are used to configure a mode of the RLC entity of the split bearer in the terminal device to the UM. when a master access network device determines that a transmission mode of a split bearer is duplicate transmission, configuring (1001, 1101), by the master access network device, a radio link control, RLC, entity of the split bearer in the master access network device to an unacknowledged mode, UM, wherein RLC entities of the split bearer are located in the master access network device, a secondary access network device, and a terminal device separately; transmitting (1002, 1102), by the master access network device, indication information to the secondary access network device, wherein the indication information is used to indicate that a transmission mode of the split bearer is duplicate transmission, and the indication information is used to configure the RLC entity of the split bearer in the secondary access network device to the UM; and transmitting (1004, 1104), by the master access network device, the indication information to the terminal device, wherein the indication information is used for the terminal device to perform duplicate transmission, wherein the method further comprises: receiving, by the master access network device, first configuration information from the secondary access network device, wherein the first configuration information indicates that a mode of the RLC entity of the split bearer in the secondary access network device is the UM; and transmitting, by the master access network device, the first configuration information and second configuration information to the terminal device, wherein the second configuration information indicates that a mode of the RLC entity of the split bearer in the master access network device is the UM, and the first configuration information and the second configuration information are used to configure a mode of the RLC entity of the split bearer in the terminal device to the UM. receiving, by the master access network device, first configuration information from the secondary access network device, wherein the first configuration information indicates that a mode of the RLC entity of the split bearer in the secondary access network device is the UM; and transmitting, by the master access network device, the first configuration information and second configuration information to the terminal device, wherein the second configuration information indicates that a mode of the RLC entity of the split bearer in the master access network device is the UM, and the first configuration information and the second configuration information are used to configure a mode of the RLC entity of the split bearer in the terminal device to the UM.