The invention provides a 
virtual machine on-line transfer method across 
virtualization data centers. The method includes that step 1, a plurality of 
virtualization data centers are deployed on a 
wide area network (WAN), and each 
virtual machine mirror file is divided into a template and user private data files, step 2, the 
virtualization data centers are connected through a virtual 
private network (VPN) of a two-tier 
bridge pattern, step 3, dirty blocks written into a disk every time are monitored in a 
virtual machine input / output (I / O) drive course on a source node, a transfer thread is created for the drive course, and the transfer thread pre-transfers the user private data files and transfers monitoring records of the dirty blocks, step 4, a transfer course of a virtual 
machine on the source node controls the pre-transfer and the transfer of the monitoring 
record, and step 5, the execution sequence of a destination node 
recovery course of the virtual 
machine is changed, a 
recovery thread is created for the 
recovery course, and the recovery thread receives information about the pre-transfer and the transfer of the monitoring records and writes the information into a storage node. The virtual 
machine on-line transfer method across the virtualization data centers can achieve 
dynamic mapping of virtual machines and resources among the plurality of virtualization data centers.