A method for receiving Acknowledgement/Negative-acknowledgement, ACK/NACK, information for carrier aggregation through an uplink component carrier in a long term evolution advanced, LTE-A, system, comprising: configuring, by a base station, a common field which is preset in one or more pieces of Downlink Control Information, DCI, wherein the common field is a transmission power control, TPC, command field which has existed in a long term evolution, LTE, system and is used in the LTE-A system for the compatibility of the LTE-A system with the LTE system; wherein each of one or more pieces of DCI includes scheduling information of a physical downlink shared channel, PDSCH, and is transmitted through a physical downlink control channel, PDCCH, corresponding to the PDSCH, wherein the PDCCH is carried on a downlink component carrier; when the downlink component carrier is a non-system-linked downlink component carrier of the uplink component carrier, a command field indicated by the common field in at least one piece of the one or more pieces of DCI is an ACK resource indication, ARI, command field; and when the downlink component carrier is a system-linked downlink component carrier of the uplink component carrier, a command field indicated by the common field in at least one piece of the one or more pieces of DCI is a transmission power control, TPC, command field; 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; sending, by the base station, the one or more pieces of DCI through the downlink component carrier to a user equipment; and receiving, by the base station, ACK/NACK information through the uplink component carrier from the user equipment. configuring, by a base station, a common field which is preset in one or more pieces of Downlink Control Information, DCI, wherein the common field is a transmission power control, TPC, command field which has existed in a long term evolution, LTE, system and is used in the LTE-A system for the compatibility of the LTE-A system with the LTE system; wherein each of one or more pieces of DCI includes scheduling information of a physical downlink shared channel, PDSCH, and is transmitted through a physical downlink control channel, PDCCH, corresponding to the PDSCH, wherein the PDCCH is carried on a downlink component carrier; when the downlink component carrier is a non-system-linked downlink component carrier of the uplink component carrier, a command field indicated by the common field in at least one piece of the one or more pieces of DCI is an ACK resource indication, ARI, command field; and when the downlink component carrier is a system-linked downlink component carrier of the uplink component carrier, a command field indicated by the common field in at least one piece of the one or more pieces of DCI is a transmission power control, TPC, command field; 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; wherein each of one or more pieces of DCI includes scheduling information of a physical downlink shared channel, PDSCH, and is transmitted through a physical downlink control channel, PDCCH, corresponding to the PDSCH, wherein the PDCCH is carried on a downlink component carrier; when the downlink component carrier is a non-system-linked downlink component carrier of the uplink component carrier, a command field indicated by the common field in at least one piece of the one or more pieces of DCI is an ACK resource indication, ARI, command field; and when the downlink component carrier is a system-linked downlink component carrier of the uplink component carrier, a command field indicated by the common field in at least one piece of the one or more pieces of DCI is a transmission power control, TPC, command field; 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; sending, by the base station, the one or more pieces of DCI through the downlink component carrier to a user equipment; and receiving, by the base station, ACK/NACK information through the uplink component carrier from the user equipment.