A method and an apparatus for constructing a random access channel of a wireless communication system, in which the method includes the following steps: setting a length of a preamble; setting a length of a cyclic prefix according to the length of the preamble; and setting a random access channel structure consisting of the preamble and the cyclic prefix. The random access channel designed by the method can be flexibly set to transmit in the UpPTS, and can satisfy the demand of a small coverage scenario in a better manner.