The present invention relates to a bandwidth request preamble sequence selecting method for bandwidth requests on a wireless access system, and to a random access procedure using the same. Also, the present invention relates to devices supporting the random access procedure. In one example of the present invention, the method for randomly accessing a wireless access system may comprise the steps of: receiving a first message containing a predefined bandwidth request index from a base station; selecting a bandwidth request preamble sequence from the predefined bandwidth request index on the basis if the properties of uplink data to be transmitted by a mobile terminal; transmitting a second message containing a predefined bandwidth request index to the base station; and transmitting the selected bandwidth request preamble sequence to the base station.