The present invention provides a virtual machine migration method, a switch, a virtual machine system. A switch receives a message sent by a server, where the message is used to enable the switch to discover a connected virtual machine interface; obtains, from the message, an identifier for indicating whether a virtual machine is migrating; and determines whether the virtual machine is a virtual machine migrated to the server according to the identifier indicating whether the virtual machine is migrated. According to the embodiments of the present invention, it may be determined whether an added virtual machine on a server is a newly created one or a migrated one.