The present application discloses a method for configuring and transmitting a key, which includes that: a) a serving cell (PCell) of UE determines a key (KeNB) used by a SCell and transmits the KeNB to the SCell; and b) the PCell transmits configuration information for configuring the SCell to the UE after receiving a response message from the SCell, and receives a response message from the UE. Or, the method includes that: a SCell of UE transmits a cell key request to an MME and receives key information from the MME; and the SCell transmits the key information received from the MME to the UE, and receives a response message from the UE. By the present application, data of the SCell is transmitted after being encrypted, so as to avoid a case that the data is decoded by other users, and further guarantee the security of the data.