A method, related apparatus, and system for virtual network migration are provided. A method provided by an embodiment of the present disclosure includes: locating a source physical node in a regional physical network; obtaining information of a virtual element corresponding to each virtual network on the source physical node and state information of each physical node in the regional physical network; determining, according to information of the virtual elements and the state information, a physical node that can execute virtual network migration in the regional physical network; reconstructing a mapping relationship between each virtual network and the regional physical network on the physical node; comparing the mapping relationships of each virtual network; selecting a mapping relationship with minimum migration consumption as a mapping relationship for executing migration; and sending, according to the mapping relationship for executing migration, a migration instruction to a physical node to execute virtual network migration.