A method and an apparatus for establishing a session between a thin client (TC) and a media gateway for media stream data transmitting are provided. The TC sends media stream transmission information of the TC to the media gateway through a virtual machine (VM), and receives media stream information of the media gateway from the VM. A session between the TC and the media gateway is established. After the session is established, the TC and the media gateway transmit media stream data directly by taste the established session.