Provided is a method for supporting retransmission in a wireless communication system by user equipment. The method may determine a transmission parameter for initial transmission of uplink data, transmit the uplink data on an uplink channel using the determined transmission parameter, and, for retransmission of the uplink data, perform multiplexing of retransmission data of the uplink data with a channel quality indicator (CQI). A radio resource for the CQI may be determined based on the transmission parameter used in an initial transmission. The method may transmit the multiplexed data on a physical uplink shared channel.