Embodiments of the present invention provide a method, a device and a system for reporting RF capability in carrier aggregation, used to reduce signaling overhead when a UE reports information. The method provided in the embodiments of the present invention includes: identifying a combination of identifiers of frequency bands that support the carrier aggregation, and generating a set of combinations of identifiers of frequency bands that support the carrier aggregation; identifying identifiers of frequency bands that do not support the carrier aggregation, and generating a set of identifiers of frequency bands that do not support the carrier aggregation; and sending the set of combinations of identifiers of frequency bands that support the carrier aggregation and the set of identifiers of frequency bands that do not support the carrier aggregation.