In a data transmission method, a terminal device receives control information, and receives data of a transport block (TB) on a first time-frequency resource; and the terminal devices obtains m code block (CB) groups in the TB, where m is a positive integer, m=min(NCB_re,NGroup_max), NCB_re is a quantity of CBs in the TB, NGroup_max is a maximum value of a quantity of CB groups, each of the m CB groups includes at least one CB, NCB_re is determined based on a TB size TBS and a maximum value of a data size of a CB, and the TBS is determined based on the control information.