1. A computing device for migrating virtual assets over a network having a first manager and a physical host connected, the physical host having a virtual machine run thereon, the computing device having a processor comprising: a registration module configured to register the physical host to a second manager in the network; a mapping module configured to create the mapping relationship of the physical host between a database of the first manager and a database of the second manager, wherein the mapping relationship of the physical host in the two databases is based on records of the physical host in the databases of both the first manager and the second manager; an instance conversion module configured to import instance data and status data of the virtual machine of the physical host from the database of the first manager into the database of the second manager; and a redirection module configured to switch the management for the physical host from the first manager to the second manager, wherein the mapping module is further configured to: extract the identity information of the physical host; locate a record of the physical host in the databases of both the first manager and the second manager based on the identity information; and establish the mapping relationship of the physical host in the two databases according to the located record.