This application relates to the field of communications technologies, and provides a data transmission method and a communications apparatus, to reduce complexity and overheads of data reception performed by a base station. The method includes: receiving information about a repetition quantity R1 corresponding to Tmax, where Tmax is a maximum transport block size allowed to be used to transmit data; determining a cyclic parameter L based on R1, where the cyclic parameter L indicates that content carried in each of a plurality of time units to which a transport block used to transmit the data is mapped is repeated in L consecutive time units, and wherein a size of the transport block used to transmit the data is Ts, and Ts