A method for determining virtual machine migration, wherein the method comprises: obtaining, by a client in a host machine, a unique identifier of a virtual machine on the host machine and an address of the host machine; determining, by the client, whether the unique identifier of the virtual machine exists in a local record, wherein the local record of the client is stored in a cache of the host machine; if the unique identifier of the virtual machine does not exist in a local record of the client, sending, by the client, a packet to a server in a network in which the host machine is located, wherein the packet carries the unique identifier of the virtual machine and the address of the host machine, the packet enables the server to determine that the virtual machine is migrated when the unique identifier of the virtual machine exists in a record of the server and the address of the host machine carried in the packet is different from a host machine address corresponding to the unique identifier of the virtual machine in the record of the server; and if the unique identifier of the virtual machine does not exist in the local record of the client, adding, by the client, the unique identifier of the virtual machine to the local record to update the local record; wherein the obtaining, by a client in a host machine, a unique identifier of a virtual machine on the host machine comprises: intercepting, by the client in the host machine, an Address Resolution Protocol, ARP, packet carrying the unique identifier of the virtual machine from the virtual machine on the host machine; and obtaining the unique identifier of the virtual machine from the intercepted packet; or, receiving, by the client in the host machine, an Address Resolution Protocol, ARP, packet carrying the unique identifier of the virtual machine from the virtual machine on the host machine and forwarded by a virtual switch on the host machine; and obtaining the unique identifier of the virtual machine from the received packet. obtaining, by a client in a host machine, a unique identifier of a virtual machine on the host machine and an address of the host machine; determining, by the client, whether the unique identifier of the virtual machine exists in a local record, wherein the local record of the client is stored in a cache of the host machine; if the unique identifier of the virtual machine does not exist in a local record of the client, sending, by the client, a packet to a server in a network in which the host machine is located, wherein the packet carries the unique identifier of the virtual machine and the address of the host machine, the packet enables the server to determine that the virtual machine is migrated when the unique identifier of the virtual machine exists in a record of the server and the address of the host machine carried in the packet is different from a host machine address corresponding to the unique identifier of the virtual machine in the record of the server; and if the unique identifier of the virtual machine does not exist in the local record of the client, adding, by the client, the unique identifier of the virtual machine to the local record to update the local record; wherein the obtaining, by a client in a host machine, a unique identifier of a virtual machine on the host machine comprises: intercepting, by the client in the host machine, an Address Resolution Protocol, ARP, packet carrying the unique identifier of the virtual machine from the virtual machine on the host machine; and obtaining the unique identifier of the virtual machine from the intercepted packet; or, receiving, by the client in the host machine, an Address Resolution Protocol, ARP, packet carrying the unique identifier of the virtual machine from the virtual machine on the host machine and forwarded by a virtual switch on the host machine; and obtaining the unique identifier of the virtual machine from the received packet. intercepting, by the client in the host machine, an Address Resolution Protocol, ARP, packet carrying the unique identifier of the virtual machine from the virtual machine on the host machine; and obtaining the unique identifier of the virtual machine from the intercepted packet; or, receiving, by the client in the host machine, an Address Resolution Protocol, ARP, packet carrying the unique identifier of the virtual machine from the virtual machine on the host machine and forwarded by a virtual switch on the host machine; and obtaining the unique identifier of the virtual machine from the received packet.