To　investigate　the　cariostatic　effects　of　the　synthetic　nano-hydroxyapatite　(HA)　on　artificial　caries,　the　nano-HA　was　synthesized　by　using　the　depositing　reaction　of　Ca　(H2PO4)2　and　the　artificial　caries　was　made　by　the　artificial　way.　The　biological　test　indicated　that　the　solution　of　nano-HA　had　dual-function　of　the　antistrike　quality　and　the　de-adhesion　quality　to　S.　mutans.　After　mineralization　of　solution　of　nano-HA　for　10　days,　the　micro　hardness　of　enamel　was　measured.　The　nano-HA　enhanced　the　micro　hardness　of　artificial　caries,　filled　up　the　voids　in　enamel,　and　improved　the　re-mineralization　of　artificial　caries.　The　rat　tooth　was　rinsed　by　gargling　way　with　the　solution　of　nano-HA　in　the　animal　test.　The　results　showed　that　the　nano-HA　led　to　the　development　of　interventions　that　could　reduce　or　modify　bacterial　colonization　of　tooth　surfaces.