The present invention provides a method and apparatus reporting a channel quality indicator (CQI) of a communication system, including: detecting a first measurement reflecting a first communication quality of the communication system, providing first reference(s) respectively corresponding to indicator level(s), providing CQI according to the indicator level(s) and a relation between the first measurement and the first reference(s), and updating one (or more) first reference according to a second measurement reflecting a second communication quality of the communication system. For example, the first measurement can represent signal to interference ratio or mutual information, and the second measurement can represent data error rate or throughput. First reference(s) can be further adjusted according to a third measurement, e.g., a power scheduling of base station, such that CQI can be updated if base station schedules additional transmission power.