A handover method for handing over a user equipment from a long term evolution network to a universal mobile telecommunication system network comprising: obtaining, by a base station, an algorithm used by a user equipment in a universal mobile telecommunication system and four least significant bits of a downlink non-access stratum count; and sending, by the base station, a handover command to the user equipment, wherein the handover command carries the algorithm used by the user equipment in the universal mobile telecommunication system and the four least significant bits of the downlink non-access stratum count for the user equipment to calculate a cipher key and an integrity key according to the four least significant bits of the downlink non-access stratum count; characterized in that obtaining, by the base station, the algorithm used by the user equipment in the universal mobile telecommunication system comprises: sending (202, 302), by the base station, a handover request message to a radio network controller, wherein the handover request message carries a security capability of the user equipment in the universal mobile telecommunication system, and the security capability of the user equipment in the universal mobile telecommunication system is obtained from an S1 application protocol message sent by a mobility management entity when the user equipment accesses a network, wherein the S1 application protocol message carries the security capability of the user equipment in the universal mobile telecommunication system; and receiving (203, 303), by the base station, a handover request acknowledgement message sent by the radio network controller, wherein the handover request acknowledgement message carries the algorithm used by the user equipment in the universal mobile telecommunication system, and the algorithm used by the user equipment in the universal mobile telecommunication system is selected by the radio network controller according to the security capability. obtaining, by a base station, an algorithm used by a user equipment in a universal mobile telecommunication system and four least significant bits of a downlink non-access stratum count; and sending, by the base station, a handover command to the user equipment, wherein the handover command carries the algorithm used by the user equipment in the universal mobile telecommunication system and the four least significant bits of the downlink non-access stratum count for the user equipment to calculate a cipher key and an integrity key according to the four least significant bits of the downlink non-access stratum count; characterized in that obtaining, by the base station, the algorithm used by the user equipment in the universal mobile telecommunication system comprises: sending (202, 302), by the base station, a handover request message to a radio network controller, wherein the handover request message carries a security capability of the user equipment in the universal mobile telecommunication system, and the security capability of the user equipment in the universal mobile telecommunication system is obtained from an S1 application protocol message sent by a mobility management entity when the user equipment accesses a network, wherein the S1 application protocol message carries the security capability of the user equipment in the universal mobile telecommunication system; and receiving (203, 303), by the base station, a handover request acknowledgement message sent by the radio network controller, wherein the handover request acknowledgement message carries the algorithm used by the user equipment in the universal mobile telecommunication system, and the algorithm used by the user equipment in the universal mobile telecommunication system is selected by the radio network controller according to the security capability. sending (202, 302), by the base station, a handover request message to a radio network controller, wherein the handover request message carries a security capability of the user equipment in the universal mobile telecommunication system, and the security capability of the user equipment in the universal mobile telecommunication system is obtained from an S1 application protocol message sent by a mobility management entity when the user equipment accesses a network, wherein the S1 application protocol message carries the security capability of the user equipment in the universal mobile telecommunication system; and receiving (203, 303), by the base station, a handover request acknowledgement message sent by the radio network controller, wherein the handover request acknowledgement message carries the algorithm used by the user equipment in the universal mobile telecommunication system, and the algorithm used by the user equipment in the universal mobile telecommunication system is selected by the radio network controller according to the security capability.