Vehicle　Navigation　System　(VNS)　is　an　important　system　in　Intelligent　Transportation　System　(ITS).　Floating　Vehicle　Data　Detection　System　is　an　important　part　of　VNS.　The　paper　introduces　the　VNS　project　in　Beijing　and　discusses　selection　of　floating　car　used　in　data　detection　system　of　Beijing.　Also　the　paper　gives　basic　structure　of　floating　vehicle　data　detection　system　and　the　functions　of　the　system.　At　last,　a　test　system　is　built　to　testify　the　practicality　of　the　floating　vehicle　data　detection　system.　The　results　show　that　the　system　works　well　and　has　good　potential　market　in　Beijing.