A method for requesting and reporting channel quality information (CQI) in a wireless portable Internet system is disclosed. Timing of a channel quality information request by a base station is determined, existence of an automatic repeat request acknowledgment (ARQ_ACK) message of downlink data is determined on requesting the channel quality information from the subscriber station, the automatic repeat request acknowledgment message and the radio resource for the channel quality report to the subscriber station is allocated, the automatic repeat request acknowledgment message and the channel quality report information is received, and a modulating and coding level of downlink data is determined by extracting the channel quality report information from the automatic repeat request acknowledgment message.