A carrier selection method and device in a carrier aggregation technology are disclosed. In embodiments, a base station obtains radio channel information of a PCC and radio channel information of an SCC that are reported by CA UE; and when the radio channel information of the SCC is greater than the radio channel information of the PCC, the base station sends, to the CA UE, an RRC reconfiguration message including information about the SCC, so that the CA UE uses the SCC as a new PCC.