There　are　many　circular-shaped　objects　in　our　daily　life.　Most　of　these　objects　usually　are　deformed　and　move　in　both　translational　and　rotational.　Under　prospective　projection,　a　circle　sometimes　deformed　into　an　ellipse.　Some　ellipse-based　tracking　algorithms　can　be　used　tracking　the　translation　when　the　contour　can　be　extracted　automatically,　but　the　rotation　can　not　be　extracted.　In　this　paper,　we　propose　an　approach　to　tracking　a　deformed　circular-shaped　object　with　translation　and　rotation　and　estimating　the　motion　parameters　accurately.　Our　idea　is　to　track　some　feature　points　on　the　object.　Then　we　build　the　geometric　relationship　between　the　feature　points　and　center　of　circle;　Finally,　we　estimate　the　motion　parameters　by　the　geometric　relation.　We　test　the　proposed　approach　using　both　simulated　data　and　practical　video　of　weight-lifting.　For　the　simulated　data,　the　average　error　for　center　of　object　is　under　1.5　pixels,　and　the　average　error　of　rotation　angle　is　under　0.50　degree.　For　the　practical　data,　we　can　obtain　the　smoothing　trajectory　of　center　of　disc.　These　experimental　results　show　that　the　proposed　approach　is　accurate　and　efficient.　©　2010　IEEE.