The present invention discloses a method and a system for non-periodic feedback in a carrier aggregation scenario. The method comprises: a base station sending a non-periodic trigger signaling to a piece of User Equipment (UE); the UE receiving the non-periodic trigger signaling, and determining a Downlink Component Carrier (DL CC) requiring feedback according to the non-periodic trigger signaling; the UE triggering a non-periodic feedback of the determined DL CC. With the present invention, the problem that it is impossible to determine which downlink component carrier is to be fed back according to the non-periodic trigger signaling in the carrier aggregation scenario is solved, uplink feedback of the DL CC that is unnecessary to be fed back is effectively reduced, the base station can adjust resource allocation according to information fed back by the UE, and the performance of downlink data transmission is ensured.