This application provides a data sending method and a terminal device. A plurality of antennas are configured for the terminal device, the plurality of antennas are configured to alternately send SRSs, the plurality of antennas include a first antenna and a second antenna. The terminal device determines to send a first SRS using the first antenna at a first moment; determines to send a second SRS using the second antenna at a second moment which is after the first moment; and determines to send first service data using the first antenna at a third moment which is after the second moment. The terminal device adjusts a transmit antenna of the first SRS as the second antenna, and adjusts a transmit antenna of the second SRS as the first antenna, to enable the transmit antenna of the second SRS to be consistent with a transmit antenna of the first service data.