An aperiodic SRS transmission method, comprising: obtaining, by a terminal device, first indication information, wherein the first indication information is used to instruct the terminal device to send an aperiodic sounding reference signal SRS on a first symbol in a first subframe; and sending, by the terminal device, the aperiodic SRS on the first symbol based on the first indication information; wherein the first indication information is information in a control message sent by an access network device and the control message information is used to instruct different terminal devices to send aperiodic SRSs on different symbols in a same subframe, or used to instruct different terminals to send aperiodic SRSs on a same symbol in different subframes, or used to instruct different terminals to send aperiodic SRSs on different symbols in different subframes; wherein the control message includes M pieces of specific indication information, and a Jth piece of specific indication information in the M pieces of specific indication information is used to instruct a Jth terminal device not to send an aperiodic SRS or instruct the Jth terminal device to send the aperiodic SRS on a Pth symbol in the first subframe, where M≥2, J≤M, and P≥1; wherein the first symbol belongs to a first symbol set, the first symbol set comprises a symbol that is in the first subframe and that is used to send an aperiodic SRS, and if the first symbol set comprises at least two symbols, any two of the at least two symbols are discontinuous in terms of time; and wherein the first symbol set is a symbol set corresponding to a first value in a first preset correspondence, the first preset correspondence comprises a correspondence between the first value and the first symbol set, the first value is used to indicate a quantity of symbols in the first subframe that are comprised in a second symbol set, and the second symbol set comprises a symbol that is in the first subframe and that is used to send downlink data, wherein the first symbol is the Pth symbol in the first symbol set. obtaining, by a terminal device, first indication information, wherein the first indication information is used to instruct the terminal device to send an aperiodic sounding reference signal SRS on a first symbol in a first subframe; and sending, by the terminal device, the aperiodic SRS on the first symbol based on the first indication information; wherein the first indication information is information in a control message sent by an access network device and the control message information is used to instruct different terminal devices to send aperiodic SRSs on different symbols in a same subframe, or used to instruct different terminals to send aperiodic SRSs on a same symbol in different subframes, or used to instruct different terminals to send aperiodic SRSs on different symbols in different subframes; wherein the control message includes M pieces of specific indication information, and a Jth piece of specific indication information in the M pieces of specific indication information is used to instruct a Jth terminal device not to send an aperiodic SRS or instruct the Jth terminal device to send the aperiodic SRS on a Pth symbol in the first subframe, where M≥2, J≤M, and P≥1; wherein the first symbol belongs to a first symbol set, the first symbol set comprises a symbol that is in the first subframe and that is used to send an aperiodic SRS, and if the first symbol set comprises at least two symbols, any two of the at least two symbols are discontinuous in terms of time; and wherein the first symbol set is a symbol set corresponding to a first value in a first preset correspondence, the first preset correspondence comprises a correspondence between the first value and the first symbol set, the first value is used to indicate a quantity of symbols in the first subframe that are comprised in a second symbol set, and the second symbol set comprises a symbol that is in the first subframe and that is used to send downlink data, wherein the first symbol is the Pth symbol in the first symbol set.