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 the number of physical resource block pairs according to the time-frequency resource; selecting, by the base station, one transport block size table from a first transport block size table and a second transport block size table, and determining a corresponding transport block size, TBS, in the selected first transport block size table or the selected second transport block size table according to a TBS index value corresponding to the determined modulation and coding scheme level and according to the determined number of physical resource block pairs, wherein any TBS in the second transport block size table is not smaller than a TBS in a same position in the first transport block size table, wherein the same position provides the same TBS index value and the same number of physical resource block pairs; sending, by the base station, service data to a user equipment by using the determined 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; wherein the selecting, by the base station, one transport block size table from a first transport block size table and a second transport block size table comprises: selecting, by the base station, one transport block size table from the first transport block size table and the second transport block size table according to a system overhead. determining, by a base station, a modulation and coding scheme level; determining, by the base station, a time-frequency resource, and determining the number of physical resource block pairs according to the time-frequency resource; selecting, by the base station, one transport block size table from a first transport block size table and a second transport block size table, and determining a corresponding transport block size, TBS, in the selected first transport block size table or the selected second transport block size table according to a TBS index value corresponding to the determined modulation and coding scheme level and according to the determined number of physical resource block pairs, wherein any TBS in the second transport block size table is not smaller than a TBS in a same position in the first transport block size table, wherein the same position provides the same TBS index value and the same number of physical resource block pairs; sending, by the base station, service data to a user equipment by using the determined 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; wherein the selecting, by the base station, one transport block size table from a first transport block size table and a second transport block size table comprises: selecting, by the base station, one transport block size table from the first transport block size table and the second transport block size table according to a system overhead.