A network interface card is provided for supporting a multi-streaming format and a method thereof. The network interface card including a host interface connected to a communication bus linked with a host CPU, a stream interface connected to an AV decoder/encoder, and a network interface connected to a network comprises a data transmission module including a tag generating unit for creating a tag for recording time information of AV streams and for adding the tag to the AV streams input through the stream I/F, an aggregator for aggregating a predetermined amount of AV streams, in which tag information is created, in order to form one packet, and a header attaching unit for creating a predetermined header including information about a type of a packet to be transferred and a transmission direction of the packet and for adding the predetermined header to the packet.