In　this　paper,　performance　characteristics　of　traffic　flow　are　analyzed　for　general　roundabout　in　Beijing.　Then　a　simplified　traffic　flow　model　is　provided　to　describe　the　weaving　sections　of　roundabout.　Because　of　no　priority　of　traffic　flow,　the　method　of　platoon　analysis　is　used　to　calculate　the　capacity　of　weaving　section　of　roundabout.　Finally,　the　capacity　of　roundabout　is　determined　using　linear　optimization　arithmetic.　Through　analysis　and　calculation　of　field　data,　the　methodology　of　roundabout　capacity　is　proved　to　be　rather　reasonable.