A core network device selection method, comprising: receiving, by an access network node, a radio resource control access stratum message sent by a terminal, wherein the access stratum message comprises a non-access stratum NAS request message and a network selection auxiliary parameter; querying, by the access network node, configuration information based on the network selection auxiliary parameter, and determining, by the access network node, a group identifier of at least one mobility management device group, wherein the configuration information comprises a correspondence between the network selection auxiliary parameter and the group identifier of a mobility management device group; determining, by the access network node, a device identifier of a target mobility management device based on the group identifier of the at least one mobility management device group; sending, by the access network node, the NAS request message to a mobility management device indicated by the device identifier of the target mobility management device; wherein the determining, by the access network node, a device identifier of a target mobility management device based on the group identifier of the at least one mobility management device comprises: selecting, by the access network node, a target mobility management device group from the at least one mobility management device group; executing, by the access network node, a NAS node selection function on each mobility management device in the target mobility management device group, and determining the device identifier of the target mobility management device; wherein the configuration information further comprises weight information of each mobility management device group corresponding to a mobility management device type; and the selecting, by the access network node, a target mobility management device group from the at least one mobility management device group comprises: selecting, by the access network node, the target mobility management device group from the at least one mobility management device group based on the weight information of each mobility management device group, of the at least one mobility management device group, corresponding to the mobility management device type. receiving, by an access network node, a radio resource control access stratum message sent by a terminal, wherein the access stratum message comprises a non-access stratum NAS request message and a network selection auxiliary parameter; querying, by the access network node, configuration information based on the network selection auxiliary parameter, and determining, by the access network node, a group identifier of at least one mobility management device group, wherein the configuration information comprises a correspondence between the network selection auxiliary parameter and the group identifier of a mobility management device group; determining, by the access network node, a device identifier of a target mobility management device based on the group identifier of the at least one mobility management device group; sending, by the access network node, the NAS request message to a mobility management device indicated by the device identifier of the target mobility management device; wherein the determining, by the access network node, a device identifier of a target mobility management device based on the group identifier of the at least one mobility management device comprises: selecting, by the access network node, a target mobility management device group from the at least one mobility management device group; executing, by the access network node, a NAS node selection function on each mobility management device in the target mobility management device group, and determining the device identifier of the target mobility management device; selecting, by the access network node, a target mobility management device group from the at least one mobility management device group; executing, by the access network node, a NAS node selection function on each mobility management device in the target mobility management device group, and determining the device identifier of the target mobility management device; wherein the configuration information further comprises weight information of each mobility management device group corresponding to a mobility management device type; and the selecting, by the access network node, a target mobility management device group from the at least one mobility management device group comprises: selecting, by the access network node, the target mobility management device group from the at least one mobility management device group based on the weight information of each mobility management device group, of the at least one mobility management device group, corresponding to the mobility management device type.