An interfacing method and system for a stream source apparatus and a display device, which includes a stream source apparatus receiving analog/digital signals from external analog/digital equipments to generate a plurality of transmission packet streams corresponding to the analog/digital signals, the stream source apparatus synthesizing a plurality of the transmission packet streams into a single synthesized transmission packet stream to transmit the synthesized transmission packet stream by wireless, a display apparatus receiving the synthesized transmission packet stream transmitted from the stream source apparatus, the display apparatus separating the synthesized transmission packet stream into a transmission packet stream corresponding to a main screen and a transmission packet stream corresponding to a sub-screen, the display apparatus decoding the transmission packet streams corresponding to the main screen and the sub-screen respectively to generate digital video/audio signals to display on a display screen by a PIP form.