Embodiments of this application provide a grant-free transmission method, a terminal device, and a network device, to improve grant-free transmission reliability. The grant-free transmission method includes: obtaining, by a terminal device, an interleaving pattern based on at least one of a cell identity of the terminal device, a terminal device identifier, time-domain resource information, and frequency-domain resource information; interleaving data based on the obtained interleaving pattern, to obtain interleaved data; and sending the interleaved data.