A method of transmitting a channel quality indicator (CQI) in a wireless communication system is provided. The method includes receiving an uplink grant on a downlink channel, the uplink grant comprising a CQI report indicator, a transport format field and a resource assignment field, the CQI report indicator indicating whether a CQI is reported, the transport format filed indicating a transport format of the CQI, the resource assignment field indicating the number of resource blocks used for reporting the CQI and transmitting the CQI on an uplink channel by using the uplink grant.