A data transmission method, comprising: determining, by a base station, a modulation and coding scheme level; determining, by the base station, a time-frequency resource, and determining a number of first physical resource block pairs according to the time-frequency resource; selecting, by the base station and from a transport block size table, a transport block size TBS corresponding to the modulation and coding scheme level and corresponding to the number of the first physical resource block pairs or a number of second physical resource block pairs, wherein the number of the second physical resource block pairs is a product of the number of the first physical resource block pairs and a set conversion factor; sending, by the base station, service data to a user equipment by adopting the selected TBS; and sending, by the base station, a system scheduling control signal to the user equipment, wherein the system scheduling control signal comprises the modulation and coding scheme level and the time-frequency resource; characterized in that the selecting, by the base station and from a transport block size table, a transport block size TBS corresponding to the modulation and coding scheme level and corresponding to the number of the first physical resource block pairs or the number of second physical resource block pairs, comprises: selecting, by the base station according to a system overhead size, the TBS corresponding to the modulation and coding scheme level and corresponding to the number of the first physical resource block pairs, or, selecting the TBS corresponding to the modulation and coding scheme level and corresponding to the number of the second physical resource block pairs. determining, by a base station, a modulation and coding scheme level; determining, by the base station, a time-frequency resource, and determining a number of first physical resource block pairs according to the time-frequency resource; selecting, by the base station and from a transport block size table, a transport block size TBS corresponding to the modulation and coding scheme level and corresponding to the number of the first physical resource block pairs or a number of second physical resource block pairs, wherein the number of the second physical resource block pairs is a product of the number of the first physical resource block pairs and a set conversion factor; sending, by the base station, service data to a user equipment by adopting the selected TBS; and sending, by the base station, a system scheduling control signal to the user equipment, wherein the system scheduling control signal comprises the modulation and coding scheme level and the time-frequency resource; characterized in that the selecting, by the base station and from a transport block size table, a transport block size TBS corresponding to the modulation and coding scheme level and corresponding to the number of the first physical resource block pairs or the number of second physical resource block pairs, comprises: selecting, by the base station according to a system overhead size, the TBS corresponding to the modulation and coding scheme level and corresponding to the number of the first physical resource block pairs, or, selecting the TBS corresponding to the modulation and coding scheme level and corresponding to the number of the second physical resource block pairs. selecting, by the base station according to a system overhead size, the TBS corresponding to the modulation and coding scheme level and corresponding to the number of the first physical resource block pairs, or, selecting the TBS corresponding to the modulation and coding scheme level and corresponding to the number of the second physical resource block pairs.