A method for performing channel sounding between terminals, comprising: sending, by a first terminal, a resource scheduling request to a network side device when the first terminal needs to communicate with a second terminal, wherein the resource scheduling request is used to request the network side device to allocate a transmission resource used for channel sounding between the first terminal and the second terminal, and the resource scheduling request carries information about the second terminal; and receiving, by the first terminal, a sounding reference signal that is sent by the second terminal on the transmission resource allocated by the network side device, and obtaining information about a channel used for communication between the first terminal and the second terminal, wherein after the sending, by a first terminal, a resource scheduling request to a network side device, the method further comprises: receiving, by the first terminal, information about the transmission resource that is sent by the network side device, and sending, by the first terminal, sounding control signaling on the transmission resource, wherein the sounding control signaling is used to trigger the second terminal to send the sounding reference signal, wherein the transmission resource is a subframe; the subframe comprises a first part that is used by the first terminal to transmit the sounding control signaling, and a second part that is used by the second terminal to transmit the sounding reference signal; and there is a guard interval between the first part and the second part of the subframe. sending, by a first terminal, a resource scheduling request to a network side device when the first terminal needs to communicate with a second terminal, wherein the resource scheduling request is used to request the network side device to allocate a transmission resource used for channel sounding between the first terminal and the second terminal, and the resource scheduling request carries information about the second terminal; and receiving, by the first terminal, a sounding reference signal that is sent by the second terminal on the transmission resource allocated by the network side device, and obtaining information about a channel used for communication between the first terminal and the second terminal, wherein after the sending, by a first terminal, a resource scheduling request to a network side device, the method further comprises: receiving, by the first terminal, information about the transmission resource that is sent by the network side device, and sending, by the first terminal, sounding control signaling on the transmission resource, wherein the sounding control signaling is used to trigger the second terminal to send the sounding reference signal, wherein the transmission resource is a subframe; the subframe comprises a first part that is used by the first terminal to transmit the sounding control signaling, and a second part that is used by the second terminal to transmit the sounding reference signal; and there is a guard interval between the first part and the second part of the subframe. receiving, by the first terminal, information about the transmission resource that is sent by the network side device, and sending, by the first terminal, sounding control signaling on the transmission resource, wherein the sounding control signaling is used to trigger the second terminal to send the sounding reference signal, wherein the transmission resource is a subframe; the subframe comprises a first part that is used by the first terminal to transmit the sounding control signaling, and a second part that is used by the second terminal to transmit the sounding reference signal; and there is a guard interval between the first part and the second part of the subframe.