A method for transmitting a signal, a terminal device, and a network device are provided, which can reduce a signal transmission delay. The method includes determining, by a terminal device, first indication information, where the first indication information is used for indicating an association relationship between a first uplink transmission opportunity used for uplink transmission and a first downlink transmission opportunity used for downlink transmission. The method also includes sending, by the terminal device, the first indication information to a network device in a time unit corresponding to the first uplink transmission opportunity.