1. A method 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 method comprising: registering the physical host to a second manager in the network; creating a mapping relationship between the physical host between a database of the first manager and a database of the second manager; importing 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; switching management for the physical host from the first manager to the second manager.