The embodiment of the invention discloses a method and device for random accessing process in a user device and a base station. The method comprises the steps of sending a message carrying user identifier information to the base station; determining whether receiving positive acknowledgement from the base station; if not, determining whether to re-transmit the message to the base station at the first re-transmission time according to the preset probability. According to the method, the random re-transmission mechanism is introduced to the random accessing process, thus the conflict of the UE and other UE during re-transmitting of the message carrying the user identifier information can be avoided; the re-transmission times can be reduced; the system resource can be saved.