Tongue　diagnosis　is　an　important　method　in　TCM.　Teeth　marks　are　objective　indexes　of　the　diagnosis　of　qi　deficiency.　One　method　on　teeth　marks　recognition　is　based　on　detecting　the　size　of　concave　regions.　The　concave　regions　are　caused　by　the　bending　of　the　tip　and　margin　of　the　tongue,　and　the　lip　shades　are　easy　to　be　misjudged　into　teeth　marks.　The　pose　and　asymmetry　of　the　tongue　body　also　affect　the　judgment.　Another　method　to　identify　teeth　marks　is　to　calculate　concavity　and　convexity　of　the　margin　of　the　tongue.　The　narrow　and　long　concave　regions　whose　concavity　is　not　deep　are　easy　to　be　misjudged　into　teeth　marks.　Accordingly,　this　paper　proposed　a　new　method　to　extract　teeth　marks　by　calculating　the　slope　of　the　margin　of　the　tongue　and　the　length　and　degree　of　the　concave　regions.　Experimental　results　demonstrate　the　effectiveness　of　the　method.