A terminal in a carrier aggregation communication network, comprising a processor, configured to communicate with a base station (210, 220, 230) in the network, and conduct selection of a new primary component carrier to be used for carrier aggregation with assistance of the base station, wherein the new primary component carrier is selected based on a rule that is decided by a distribution mode in the case that a distribution of coverages of different available carriers corresponding to a position of the terminal accords with a predetermined distribution mode, wherein the predetermined distribution mode and corresponding rule is one of: the predetermined distribution mode is that the coverages of different available carriers are substantially the same, and the rule comprises taking each available carrier as a candidate primary component carrier; and the predetermined distribution mode is that the coverage of an available carrier is larger than the coverage of another available carrier and substantially contains the coverage of another available carrier, and the rule comprises determining a candidate primary component carrier according to the size of the coverage of each available carrier, the new primary component carrier is further selected based on signal quality of the available carriers, a factor of coverages of different available carriers has a higher priority than a factor of signal quality of available carriers for selecting the new primary component carrier; wherein the processor is further configured to initiate a random access process to access to a new base station to which the new primary component carrier belongs to access the new primary component carrier, the random access process is competitive among multiple terminals; and add a new secondary component carrier to aggregate with the new primary component carrier based on radio resource control reconfiguration information from the new base station and continue to use previous configuration of MAC layer and security key, the radio resource control reconfiguration information including radio resource configuration information of the new secondary component carrier. the predetermined distribution mode is that the coverages of different available carriers are substantially the same, and the rule comprises taking each available carrier as a candidate primary component carrier; and the predetermined distribution mode is that the coverage of an available carrier is larger than the coverage of another available carrier and substantially contains the coverage of another available carrier, and the rule comprises determining a candidate primary component carrier according to the size of the coverage of each available carrier, the new primary component carrier is further selected based on signal quality of the available carriers, a factor of coverages of different available carriers has a higher priority than a factor of signal quality of available carriers for selecting the new primary component carrier; wherein the processor is further configured to initiate a random access process to access to a new base station to which the new primary component carrier belongs to access the new primary component carrier, the random access process is competitive among multiple terminals; and add a new secondary component carrier to aggregate with the new primary component carrier based on radio resource control reconfiguration information from the new base station and continue to use previous configuration of MAC layer and security key, the radio resource control reconfiguration information including radio resource configuration information of the new secondary component carrier.