Embodiments of this application provide a data transmission method, a terminal device, and a network device. The method includes: receiving, by a terminal device, a first indication sent by a network device; receiving, by the terminal device, downlink data based on the first indication, and generating feedback information of the downlink data; receiving, by the terminal device, a second indication sent by the network device, where the second indication indicates a start location of an uplink time unit; determining, by the terminal device based on the first indication and the second indication, a resource location for sending the feedback information; and sending, by the terminal device, the feedback information at the resource location.