A packet data unit, PDU, session processing method, comprising: receiving, by a access and mobility management function, AMF, network element, a message from a terminal through a first network, wherein the message comprises handover indication information, and the handover indication information instructs the AMF network element to hand over a PDU session from a second network to the first network; characterized by processing, by the AMF network element, the handover of the PDU session based on identifier information of a session management network element corresponding to the PDU session comprising: obtaining, by the AMF network element, the identifier information of the session management network element from a data management network element; and determining, by the AMF network element based on the identifier information of the session management network element, that the AMF network element and the session management network element belong to a same public land mobile network, PLMN and establishing, by the AMF network element, the PDU session in the first network; or determining, by the AMF network element based on the identifier information of the session management network element, that the AMF network element and the session management network element do not belong to a same PLMN and rejecting, by the AMF network element, establishment of the PDU session in the first network. receiving, by a access and mobility management function, AMF, network element, a message from a terminal through a first network, wherein the message comprises handover indication information, and the handover indication information instructs the AMF network element to hand over a PDU session from a second network to the first network; characterized by processing, by the AMF network element, the handover of the PDU session based on identifier information of a session management network element corresponding to the PDU session comprising: obtaining, by the AMF network element, the identifier information of the session management network element from a data management network element; and determining, by the AMF network element based on the identifier information of the session management network element, that the AMF network element and the session management network element belong to a same public land mobile network, PLMN and establishing, by the AMF network element, the PDU session in the first network; or determining, by the AMF network element based on the identifier information of the session management network element, that the AMF network element and the session management network element do not belong to a same PLMN and rejecting, by the AMF network element, establishment of the PDU session in the first network. obtaining, by the AMF network element, the identifier information of the session management network element from a data management network element; and determining, by the AMF network element based on the identifier information of the session management network element, that the AMF network element and the session management network element belong to a same public land mobile network, PLMN and establishing, by the AMF network element, the PDU session in the first network; or determining, by the AMF network element based on the identifier information of the session management network element, that the AMF network element and the session management network element do not belong to a same PLMN and rejecting, by the AMF network element, establishment of the PDU session in the first network.