A method for feeding back Acknowledgement/Negative-acknowledgement, ACK/NACK, information for carrier aggregation, characterized by comprising: configuring, by a base station, a common field in at least one piece of Downlink Control Information, DCI, transmitted by a system-linked downlink component carrier as a transmission power control, TPC, command field and configuring, by the base station, a common field in at least one piece of DCI transmitted by a non-system-linked downlink component carrier as an ACK resource indication, ARI, command field; assigning, by the base station, an uplink ACK channel resource in an uplink component carrier for a user equipment, comprising: assigning an uplink ACK channel resource to a PDSCH transmission by reserving an uplink ACK channel resource in one uplink component carrier for each physical downlink control channel, PDCCH, transmitted over a system-linked downlink component carrier, wherein the assigned ACK channel resource is to be obtained through implicit mapping from the corresponding PDCCH; and notifying, through high-level signaling, a group of uplink ACK channel resources for PDSCH transmission whose corresponding PDCCH is transmitted over a non-system-linked downlink component carrier; wherein if an uplink ACK channel resource implicitly mapped from a PDCCH is reserved on one uplink component carrier for a certain downlink component carrier, the downlink component carrier is a system-linked downlink component carrier of the uplink component carrier; and sending, by the base station, the DCI to the user equipment. configuring, by a base station, a common field in at least one piece of Downlink Control Information, DCI, transmitted by a system-linked downlink component carrier as a transmission power control, TPC, command field and configuring, by the base station, a common field in at least one piece of DCI transmitted by a non-system-linked downlink component carrier as an ACK resource indication, ARI, command field; assigning, by the base station, an uplink ACK channel resource in an uplink component carrier for a user equipment, comprising: assigning an uplink ACK channel resource to a PDSCH transmission by reserving an uplink ACK channel resource in one uplink component carrier for each physical downlink control channel, PDCCH, transmitted over a system-linked downlink component carrier, wherein the assigned ACK channel resource is to be obtained through implicit mapping from the corresponding PDCCH; and notifying, through high-level signaling, a group of uplink ACK channel resources for PDSCH transmission whose corresponding PDCCH is transmitted over a non-system-linked downlink component carrier; assigning an uplink ACK channel resource to a PDSCH transmission by reserving an uplink ACK channel resource in one uplink component carrier for each physical downlink control channel, PDCCH, transmitted over a system-linked downlink component carrier, wherein the assigned ACK channel resource is to be obtained through implicit mapping from the corresponding PDCCH; and notifying, through high-level signaling, a group of uplink ACK channel resources for PDSCH transmission whose corresponding PDCCH is transmitted over a non-system-linked downlink component carrier; wherein if an uplink ACK channel resource implicitly mapped from a PDCCH is reserved on one uplink component carrier for a certain downlink component carrier, the downlink component carrier is a system-linked downlink component carrier of the uplink component carrier; and sending, by the base station, the DCI to the user equipment.