An embodiment of the present disclosure provides a preamble configuration method on an unlicensed carrier, the method includes: configuring a Physical Random Access Channel ( PRACH) configuration message, the PRACH configuration message including subframe location information, first Clear Channel Assessment (CCA) interval location information, a channel detection mechanism, preamble format information, and preamble sending location information. The subframe location information indicates a location of a subframe where M to-be-transmitted preambles are located. The first CCA interval location information represents a location of a CCA interval before each preamble in the M to-be-transmitted preambles on the subframe or on a previous subframe of the subframe. The channel detection mechanism is used for indicating whether user equipment detects that the unlicensed carrier is in an idle state. The preamble format information indicates that the to-be-transmitted preambles are format 4 preambles. Sending control signaling carrying the PRACH configuration message to the user equipment. The present disclosure also provides a preamble transmission method and a related device. The present disclosure can reduce the time delay of access.