It　is　of　important　practical　significance　for　the　drivers　under　emergency　to　make　accurate　judgment　and　operation　in　time.　In　this　paper,　Freecod　data　collection　system,　dynamic　GPS　are　used　in　the　research　of　driver＇s　braking　operation　under　emergency　in　the　Transportation　Communication　Trial　Field.　In　the　first　place,　the　relationship　between　steering　velocity　and　the　distance　from　obstructions,　as　well　as　car　speed,　has　been　analyzed;　in　the　second　place,　the　model　of　the　relationship　has　been　established;　at　last,　the　model　has　been　validated　whose　result　means　a　lot　for　the　management　of　the　driver＇s　safety　and　traffic　safety.　©　2011　Chinese　Assoc　of　Automati.