In　this　paper,　we　establish　a　dynamical　model　of　four　degree-of-freedom　for　an　automotive　disc　brake　system.　We　study　stick-slip　oscillations　in　both　circumferential　direction　and　radial　direction　of　the　brake　rotor.　The　stick-slip　phenomena　are　investigated　and　a　complex　process　has　been　observed　that　the　system　changes　from　the　periodical　motion　with　no　stick　phenomena　to　the　periodical　or　chaotic　motion　with　one　or　more　stick　phenomena.　By　numerical　simulation,　some　periodical　portraits　and　chaotic　portraits　are　obtained.　The　numerical　results　show　that　the　rotor＇s　angle　velocity　and　the　nature　frequency　of　the　rotor　have　much　effect　on　the　motion　of　the　system.　The　results　also　indicate　that　the　pad　and　the　rotor　keep　stick　in　radial　direction　most　of　the　time,　but　have　relative　motion　between　times.