50　typical　signalized　intersections　are　selected　as　objects　of　study　in　Beijing.　Through　the　regression　of　saturation　headway　in　different　lane,　the　principle　is　brought　forward　of　how　to　distinguish　the　state　of　following　car　after　the　green　light　start,　with　which　we　ascertain　the　saturation　headway　and　saturation　volume　rate　in　different　lane.　Concepts　of　＂lane　group＂　and　＂benchmark　lane＂　are　introduced　in　this　study,　and　the　capacity　model　of　lane　group　and　benchmark　lane　are　also　finished,　hoping　to　make　the　lane　group　as　a　whole　unit　to　calculate　the　signalized　intersection　capacity.　This　method　may　be　suitable　for　the　actual　situation　of　Chinese.