The invention discloses a virtual machine migration method of an energy-saving data center. In all physical machines in the existing virtual machine mapping schemes, physical machines with the fewest virtual machines are selected sequentially to conduct virtual machine migration, during migration, the virtual machines with the maximum business flow are selected sequentially, and the physical machines with the remaining resource capacity capable of meeting the virtual machines are found. If a plurality of physical machines meeting the requirements occur, cost generated by the virtual machine business flow when the virtual machines are migrated to the physical machines is calculated, the physical machine with the minimum cost is selected to conduct migration till the virtual machines can not find the physical machines meeting capacity requirements, and virtual machine migration is finished. By means of the method, idle physical machines are turned off through virtual machine migration to save energy, business flow is considered comprehensively, and data center network energy consumption is further reduced. Virtual machine migration is finished through migration times as few as possible, and energy consumption brought by migration is optimized.