A method for sending a sounding reference signal, SRS, in a time division duplex system, the method comprising: receiving, by a terminal device, from a network device, downlink control information, DCI, on a physical downlink control channel, PDCCH, wherein the DCI comprises first indication information, and the first indication information is used to trigger the terminal device to send an SRS; and determining, by the terminal device and based on the DCI and/or higher layer signaling, a first time interval in a plurality of candidate first time intervals corresponding to a first subcarrier spacing, wherein the first subcarrier spacing is one of the following plurality of subcarrier spacings: a 15kilohertz, kHz, subcarrier spacing, a 30kHz subcarrier spacing, a 60kHz subcarrier spacing, and a 120kHz subcarrier spacing; and a correspondence between the first subcarrier spacing and the first time interval meets at least one of the following conditions: a first time interval corresponding to the 15kHz subcarrier spacing is less than or equal to eight symbols, a first time interval corresponding to the 30kHz subcarrier spacing is less than or equal to 12 symbols, a first time interval corresponding to the 60kHz subcarrier spacing is less than or equal to 24 symbols, and a first time interval corresponding to the 120kHz subcarrier spacing is less than or equal to 42 symbols; characterized in that the first time interval is used, by the terminal device, to determine whether the first indication information is valid; the terminal device sends the SRS, to the network device, triggered by the first indication information if it is determined that the first indication information is valid. receiving, by a terminal device, from a network device, downlink control information, DCI, on a physical downlink control channel, PDCCH, wherein the DCI comprises first indication information, and the first indication information is used to trigger the terminal device to send an SRS; and determining, by the terminal device and based on the DCI and/or higher layer signaling, a first time interval in a plurality of candidate first time intervals corresponding to a first subcarrier spacing, wherein the first subcarrier spacing is one of the following plurality of subcarrier spacings: a 15kilohertz, kHz, subcarrier spacing, a 30kHz subcarrier spacing, a 60kHz subcarrier spacing, and a 120kHz subcarrier spacing; and a correspondence between the first subcarrier spacing and the first time interval meets at least one of the following conditions: a first time interval corresponding to the 15kHz subcarrier spacing is less than or equal to eight symbols, a first time interval corresponding to the 30kHz subcarrier spacing is less than or equal to 12 symbols, a first time interval corresponding to the 60kHz subcarrier spacing is less than or equal to 24 symbols, and a first time interval corresponding to the 120kHz subcarrier spacing is less than or equal to 42 symbols; characterized in that the first time interval is used, by the terminal device, to determine whether the first indication information is valid; the terminal device sends the SRS, to the network device, triggered by the first indication information if it is determined that the first indication information is valid.