A method for transmitting a sounding reference signal and a terminal device are provided. The method includes: receiving, by the terminal device, SRS configuration information from a network device; determining, based on one or more of an SRS bandwidth configuration parameter, a sequence number nSRS of a quantity of SRS transmissions, a quantity Λ of antenna ports, and the received SRS configuration information, an index α(nSRS) corresponding to an antenna port used to transmit an SRS; selecting the antenna port with the index of α(nSRS) from indexes corresponding to the Λ antenna ports; and transmitting the SRS through the antenna port with the index of α(nSRS) during an nSRSth SRS transmission. nSRS is an integer greater than or equal to 0, Λ is a positive integer greater than or equal to 4, and a symbol * indicates a multiplication operation.