Embodiments disclose an uplink data transmission method and apparatus. The method includes: determining M transmission areas allocated to a terminal device, and generating first information used to indicate the M transmission areas, where M is a positive integer, and the transmission area represents an air interface time-frequency resource that includes a time range and a frequency range that are specified by a communications system. The method also includes determining, for each transmission area of the M transmission areas, second information used to indicate a transport block size. The method also includes sending an indication message to the terminal device, so that the terminal device transmits uplink data according to the indication message, where the indication message includes the first information and the second information.