This application discloses a grant-free transmission method, a network device, and a terminal device. The method includes: detecting, by a network device, a pilot sequence used by a terminal device for uplink transmission; determining, by the network device, a pilot sequence index of the pilot sequence based on the pilot sequence and a correspondence between the pilot sequence and the pilot sequence index; and sending, by the network device, information about a feedback result of the uplink transmission to the terminal device based on the pilot sequence index.