A method and an apparatus for performing communication in wireless communication system are provided. The method includes receiving random access channel (RACH) configuration information from a base station (BS), in case that a type of a random access is identified as 2-step contention free based on the RACH configuration information, selecting a synchronization signal block (SSB) with synchronization signal-reference signal received power (SS-RSRP) above a configured threshold among SSBs, identifying a random access occasion corresponding to the selected SSB, identifying a physical uplink shared channel (PUSCH) occasion corresponding to a RACH slot of the selected random access occasion from PUSCH occasions configured based on PUSCH resource configuration information included in the RACH configuration information, and performing msgA transmission based on the identified random access occasion and the identified PUSCH occasion.