A data transmission method and an apparatus used in a virtual switch technology are provided, and the method includes: receiving an IO request of a virtual machine VM for accessing a file or a disk, and When the IO request is to be sent to a physical NIC by using a user mode Open vSwitch (OVS), converting the IO request into an Internet Small Computer Systems Interface (iSCSI) command in a user mode, and then sending the iSCSI command to the user mode OVS, where the user mode OVS sends the iSCSI command to the physical NIC.