The　aim　of　this　study　is　to　describe　the　remineralization　effect　of　the　nano-HA　toothpaste　on　artificial　caries.　The　artificial　dental　caries　is　made　using　sour　solution.　The　demineralized　teeth　specimen　is　put　into　five　kinds　of　toothpaste　solution　respectively　for　5　days　and　10　days,　which　are:　solution　of　containing　needle　like　nano-HA,　solution　of　containing　spherical　nano-HA,　solution　of　general　HA,　fluorine　sodium　solution　and　physiological　saline.　The　hardness　of　specimen　is　measured　and　the　surface　morphology　is　characterized　by　SEM.　The　remineralized　test　indicates　that　the　nano-HA　toothpaste　can　enhance　the　hardness　of　artificial　caries　and　improve　the　remineralization　of　artificial　caries.　The　SEM　analysis　shows　that　the　cavities　and　defects　of　enamel　surface　are　decreased　and　many　mineral　salts　are　sedimentated,　which　indicate　that　the　nano-HA　could　promote　remineralization　for　the　demineralized　enamel.