The present invention provides a method, a base station, and a user equipment for feeding back ACK/NACK information for carrier aggregation. The method includes: configuring a common field preset in DCI as at least one type of command field related to ACK/NACK feedback of at least two types of command fields related to ACK/NACK feedback, where the common field can be configured as the command fields related to ACK/NACK feedback; and sending the DCI to a user equipment, so that the user equipment feeds back ACK/NACK information according to the DCI. The present invention may realize backward compatibility of the ACK/NACK information feedback with an LTE system in carrier aggregation.