Image　segmentation　and　image　denoising　are　two　important　and　fundamental　topics　in　the　field　of　image　processing.　Geometric　active　contour　model　based　on　level　set　method　can　deal　with　the　problem　of　image　segmentation,　but　it　does　not　consider　the　problem　of　image　denoising.　In　this　paper,　a　new　diffusion　equation　model　for　noisy　image　segmentation　is　proposed　by　incorporating　some　classical　diffusion　equation　denoising　models　into　the　segmental　process.　An　assumption　about　the　connection　between　the　image　intensity　and　level　set　function　is　given　firstly.　Some　classical　denoising　models　are　employed　to　describe　the　evolution　of　level　set　function　secondly.　The　final　nonlinear　diffusion　equation　model　for　noisy　image　segmentation　is　built　thirdly.　Then　image　segmentation　and　image　denoising　are　combined　in　a　united　framework.　The　segmental　results　can　be　presented　by　level　set　function.　Experimental　results　show　that　the　newmodel　has　the　advantage　of　noise　resistance　and　is　superior　to　traditional　segmentation　model.