This application discloses a grant-free transmission method, a terminal device, and a network device. The method includes: sending, by a terminal device, control information to a network device on a grant-free transmission resource; and receiving, by the terminal device, feedback information that is sent by the network device based on the control information. In this way, the terminal device sends the control information to the network device on the grant-free transmission resource, so that in a data transmission process, the terminal device can obtain a transmission parameter or resource information and properly adjust the transmission process of the terminal device in a timely manner.