Shipbornc Automatic Identification System (AIS) will be an important marine equipment used for dcntification, surveillance and communication in the 21st century, which is currently being rcsearched indeveloped countries. A technioal scheme of AIS is proposed in this paper. The main compoenent of the AIS is a broadcast transponder, and the core technology is a VHF radio data link with highh capacity, named STDMA (Self-organized Time Divison Multiple Access). The ships installed the AIS, which wil automatically and peniodically broadcast their positions and identities in the marine VHF channels, can be eisplayed on a screen of an ECDIS on board or in VTS centers. The AIS is able to support not only broadcast service but also point-to-point communication service.