Embodiments of this application provide a method for sending downlink control information, a terminal device, and a network device, and relate to the communications field, to resolve problems of low flexibility and low reliability of a system DCI configuration. The method includes: receiving DCI for scheduling downlink data to be transmitted as one codeword, wherein the DCI comprises a value of a set of values each indicating a corresponding quantity of layers of the one codeword and one or more antenna ports used for sending the one codeword, and wherein the set of values comprises: a first value indicating that the quantity of layers of the one codeword is 2, and a first antenna port and a second antenna port are used for sending the one codeword, and a second value indicating that the quantity of layers of the one codeword is 2 and a third antenna port and a fourth antenna port are used for sending the one codeword.