A method, a system and a device for indicating and transmitting the preamble are used to solve the problem existing in the prior art, which reduces the resource utilization efficiency due to that the user equipment (UE) sends the preamble to the evolution base station through the physical random access channel (PRACH) selected by itself in the present random access. The method includes: determining the channel signature associated with the PRACH assigned to the terminal side; sending the determined channel signature to the terminal side, and indicating the terminal side to transmit the preamble using the PRACH associated with the channel signature. Adopting said method can improve the resource utilization efficiency.