The present application provides a method for transmitting data and a terminal device. The method includes: a terminal device receiving first signaling, wherein the first signaling indicates the terminal device to transmit a first physical uplink channel on a first resource; the terminal device determining whether a transmission parameter used for transmitting the first physical uplink channel satisfies a preset condition; and the terminal device carrying data of a first type on the first physical uplink channel and performing transmission when the transmission parameter satisfies the preset condition, wherein the data of the first type of data is data based on grant-free transmission.