The　implementation　of　traffic　guidance　system　requires　the　contribution　of　effective　and　reliable　data　communication　mode　to　utilize　real-time　traffic　information.　However,　current　static　traffic　route　guidance　system　can　not　obtain　and　update　real-time　traffic　information.　The　traffic　condition　data　collected　by　probe　cars　are　transmitted　to　traffic　guidance　information　centre,　accordingly　up-to-date　values　of　dynamic　road　weight　and　other　guidance　data　are　sent　to　OBUs(onboard　units)　in　the　car　over　network.　It　is　submitted　that　real　time　traffic　guidance　system　based　on　Mobitex　improves　performance　of　route　guidance　and　programming　via　feasible　and　reliable　data　transmission.　The　designed　communication　protocol　enables　traffic　guidance　system　to　collect,　transmit,　process　and　broadcast　real-time　traffic　data,　which　provides　an　applicable　means　by　guaranteeing　timeliness　and　reliability　of　dynamic　traffic　information　service.