A signal transmission method, a signal transmission control method, a user equipment (UE), and a base station, where the signal transmission method includes performing, by UE, channel detection, and sending, by the UE, uplink data when a result of the channel detection is that a channel is available, where the uplink data includes one or more subframes, at least one subframe includes a sounding reference signal (SRS), and the SRS is located at a start location of the subframe. The signal transmission control method includes sending, by a base station, SRS configuration information to the UE radio resource control (RRC) signaling or physical downlink control signaling (DCI) such that the UE sends an SRS based on the SRS configuration information. Hence, utilization of a channel can be significantly improved.