Tongue　Diagnosis　plays　an　important　role　in　the　Inspection　of　Traditional　Chinese　medicine.　In　order　to　analyze　the　features　of　tongue　body　automatically,　tongue　segmentation　should　be　done　firstly.　Because　of　the　texture　complexity　of　the　tongue　and　the　lip,　it　is　difficult　to　abstract　the　accurate　contour　of　the　tongue　body　only　with　Snakes　model.　A　knowledge-based　arithmetic　is　adapted　which　makes　full　use　of　the　tongue　body＇s　information,　such　as　position　and　color.