A data transmission method, comprising: obtaining, by a first communication device, a first target block error rate, BLER,; receiving, by the first communication device, a channel quality indicator, CQI, from the second communication device, wherein the CQI is used to indicate quality of a channel between the first communication device and the second communication device; determining, by the first communication device, a modulation and coding scheme, MCS, of to-be-transmitted data according to a preset table and the CQI, wherein the preset table indicates a mapping between the CQI and the MCS and corresponds to the first target BLER; coding and modulating, by the first communication device, the to-be-transmitted data based on the MCS; and sending, by the first communication device, the MCS and the coded and modulated to-be-transmitted data to the second communication device; characterized in that: the obtaining, by a first communications device, a first target BLER comprises: determining, by the first communications device, the first target BLER from two target BLERs based on a delay requirement and a reliability requirement of the to-be-transmitted data wherein a lower delay requirement of the to-be-transmitted data indicates a lower target BLER and a higher reliability requirement of the to be transmitted data indicates a lower target BLER, wherein the two target BLERs are 0.1 and 0.00001; wherein different target BLERs correspond to different preset tables. obtaining, by a first communication device, a first target block error rate, BLER,; receiving, by the first communication device, a channel quality indicator, CQI, from the second communication device, wherein the CQI is used to indicate quality of a channel between the first communication device and the second communication device; determining, by the first communication device, a modulation and coding scheme, MCS, of to-be-transmitted data according to a preset table and the CQI, wherein the preset table indicates a mapping between the CQI and the MCS and corresponds to the first target BLER; coding and modulating, by the first communication device, the to-be-transmitted data based on the MCS; and sending, by the first communication device, the MCS and the coded and modulated to-be-transmitted data to the second communication device; characterized in that: the obtaining, by a first communications device, a first target BLER comprises: determining, by the first communications device, the first target BLER from two target BLERs based on a delay requirement and a reliability requirement of the to-be-transmitted data wherein a lower delay requirement of the to-be-transmitted data indicates a lower target BLER and a higher reliability requirement of the to be transmitted data indicates a lower target BLER, wherein the two target BLERs are 0.1 and 0.00001; wherein different target BLERs correspond to different preset tables. determining, by the first communications device, the first target BLER from two target BLERs based on a delay requirement and a reliability requirement of the to-be-transmitted data wherein a lower delay requirement of the to-be-transmitted data indicates a lower target BLER and a higher reliability requirement of the to be transmitted data indicates a lower target BLER, wherein the two target BLERs are 0.1 and 0.00001; wherein different target BLERs correspond to different preset tables.