Embodiments of the present invention disclose a function migration method, an apparatus, and a system, which are applied to the communications field, and a network can actively transfer a function service of a user between network nodes. The method is specifically: sending, by a first network node, a function migration request to the second network node; receiving, by the first network node, a function migration response sent by the second network node; and sending, by the first network node, a migration execution instruction to the second network node, where the migration execution instruction is used to instruct the second network node to perform the first function service on the first user. The present invention is used by a network to transfer a function service of a user between network nodes.