A data transmission method, comprising: sending, by a terminal device, a message 1 to a first network device, wherein the message 1 comprises a random access preamble, wherein the random access preamble is useable by the first network device to send a random access response comprising a message 2 to the terminal device upon successful detection of the random access preamble by the first network device; receiving, by the terminal device, downlink control information DCI and the message 2 scheduled by the DCI from the first network device, wherein the message 2 comprises downlink data, the DCI or the message 2 comprises first information, and the first information is used to schedule acknowledgement ACK/negative acknowledgement NACK feedback information of the message 2; and sending, by the terminal device, the ACK/NACK feedback information to the first network device based on the first information; wherein the sending, by the terminal device, the ACK/NACK feedback information to the first network device based on the first information comprises: determining, by the terminal device, a time-frequency resource, a subcarrier spacing, and a repetition quantity that are of the ACK/NACK feedback information; and sending, by the terminal device, the ACK/NACK feedback information based on the time-frequency resource, the subcarrier spacing, and the repetition quantity, wherein the first information comprises the following: first indication information, wherein the first indication information is used to determine the subcarrier spacing of subcarriers for transmitting the ACK/NACK feedback information; and second indication information, wherein the second indication information is used to determine the repetition quantity of the ACK/NACK feedback information. sending, by a terminal device, a message 1 to a first network device, wherein the message 1 comprises a random access preamble, wherein the random access preamble is useable by the first network device to send a random access response comprising a message 2 to the terminal device upon successful detection of the random access preamble by the first network device; receiving, by the terminal device, downlink control information DCI and the message 2 scheduled by the DCI from the first network device, wherein the message 2 comprises downlink data, the DCI or the message 2 comprises first information, and the first information is used to schedule acknowledgement ACK/negative acknowledgement NACK feedback information of the message 2; and sending, by the terminal device, the ACK/NACK feedback information to the first network device based on the first information; wherein the sending, by the terminal device, the ACK/NACK feedback information to the first network device based on the first information comprises: determining, by the terminal device, a time-frequency resource, a subcarrier spacing, and a repetition quantity that are of the ACK/NACK feedback information; and sending, by the terminal device, the ACK/NACK feedback information based on the time-frequency resource, the subcarrier spacing, and the repetition quantity, wherein the first information comprises the following: first indication information, wherein the first indication information is used to determine the subcarrier spacing of subcarriers for transmitting the ACK/NACK feedback information; and second indication information, wherein the second indication information is used to determine the repetition quantity of the ACK/NACK feedback information. determining, by the terminal device, a time-frequency resource, a subcarrier spacing, and a repetition quantity that are of the ACK/NACK feedback information; and sending, by the terminal device, the ACK/NACK feedback information based on the time-frequency resource, the subcarrier spacing, and the repetition quantity, wherein the first information comprises the following: first indication information, wherein the first indication information is used to determine the subcarrier spacing of subcarriers for transmitting the ACK/NACK feedback information; and second indication information, wherein the second indication information is used to determine the repetition quantity of the ACK/NACK feedback information. first indication information, wherein the first indication information is used to determine the subcarrier spacing of subcarriers for transmitting the ACK/NACK feedback information; and second indication information, wherein the second indication information is used to determine the repetition quantity of the ACK/NACK feedback information.