A mobility management method, performed by a UE, comprising: receiving core network information about each cell from a network side device, the core network information being used to indicate a type of a core network; and when the UE is in a connected state, subsequent to receiving the core network information about each cell from the network side device, the mobility management method further comprises: receiving a handover command message from the network side device in a source cell, the handover command message being used to indicate a target cell for handover to the UE; and performing cell handover in accordance with the target cell indicated in the handover command message; wherein the source cell is an evolved Long Term Evolution, eLTE, cell connected to a 5 th -Generation, 5G, core network, a 5G New Radio, NR, cell or an LTE cell, and the target cell is an eLTE cell connected to the 5G core network, a 5G NR cell or an LTE cell; characterized in that, when the source cell is an eLTE cell and the target cell is an NR cell, the handover command message is an Evolved Universal Mobile Telecommunications System, UMTS, Terrestrial Radio Access Network, EUTRAN, handover command message carrying an air-interface configuration parameter and an NR air-interface Radio Access Technique, RAT, type indicator of the target cell, and the EUTRAN handover command message carries information about core-network-related security parameters. receiving core network information about each cell from a network side device, the core network information being used to indicate a type of a core network; and when the UE is in a connected state, subsequent to receiving the core network information about each cell from the network side device, the mobility management method further comprises: receiving a handover command message from the network side device in a source cell, the handover command message being used to indicate a target cell for handover to the UE; and performing cell handover in accordance with the target cell indicated in the handover command message; wherein the source cell is an evolved Long Term Evolution, eLTE, cell connected to a 5 th -Generation, 5G, core network, a 5G New Radio, NR, cell or an LTE cell, and the target cell is an eLTE cell connected to the 5G core network, a 5G NR cell or an LTE cell; characterized in that, when the source cell is an eLTE cell and the target cell is an NR cell, the handover command message is an Evolved Universal Mobile Telecommunications System, UMTS, Terrestrial Radio Access Network, EUTRAN, handover command message carrying an air-interface configuration parameter and an NR air-interface Radio Access Technique, RAT, type indicator of the target cell, and the EUTRAN handover command message carries information about core-network-related security parameters. receiving a handover command message from the network side device in a source cell, the handover command message being used to indicate a target cell for handover to the UE; and performing cell handover in accordance with the target cell indicated in the handover command message; wherein the source cell is an evolved Long Term Evolution, eLTE, cell connected to a 5 th -Generation, 5G, core network, a 5G New Radio, NR, cell or an LTE cell, and the target cell is an eLTE cell connected to the 5G core network, a 5G NR cell or an LTE cell; characterized in that, when the source cell is an eLTE cell and the target cell is an NR cell, the handover command message is an Evolved Universal Mobile Telecommunications System, UMTS, Terrestrial Radio Access Network, EUTRAN, handover command message carrying an air-interface configuration parameter and an NR air-interface Radio Access Technique, RAT, type indicator of the target cell, and the EUTRAN handover command message carries information about core-network-related security parameters.