The embodiment of the present invention discloses an ACK/NACK information feedback method for downlink data. The method comprises the steps of: acquiring processing capability information about a userequipment, and reporting the processing capability information to a base station; acquiring data information about a downlink data packet; calculating, according to the processing capability information and the data information, a basic delay time required by the user equipment for performing data decoding and ACK/NACK information coding on the downlink data packet; receiving an extra delay timeissued by the base station for the downlink data packet, wherein the extra delay time is used for indicating the position of a subframe for feeding back the ACK/NACK information corresponding to the downlink data packet; and selecting, according to the sum of the basic delay time and the extra delay time, a corresponding subframe to feed back the ACK/NACK information corresponding to the downlinkdata packet. Further disclosed are a base station using the method, and a user equipment. The method can effectively reduce a data transmission delay.