A method for transmitting a random access preamble at a user equipment in a wireless communication system is disclosed. The method includes determining a random access sequence transmission period using a random access sequence, configuring a random access preamble by inserting a cyclic prefix at a front of the random access sequence transmission period and a guard time at an end of the random access sequence transmission period, and transmitting the random access preamble on a random access channel to a base station. The random access preamble is configured by repeating the random access sequence a predetermined number of times, if the length of the random access sequence is smaller than the random access sequence transmission period.