Abstract: A method, an apparatus and a system for migrating virtual machines are provided. The method includes: a switch detecting whether a quantity of the virtual machines connected with a first virtual machine bearing server is less than a first threshold; when the quantity of the virtual machines is less than the first threshold, the switch requesting a virtual machine management server to migrate the virtual machines connected with the first virtual machine bearing server to another virtual machine bearing server or other virtual machine bearing servers. The embodiments of the disclosure solve the problem that packet loss is possibly caused by virtual machine migration methods in relevant technologies, and guarantee the smooth progress of services while reducing the energy consumption of data centre network devices.