Fe3O4　nanoparticle　was　synthesized　in　the　solution　involving　water　and　ethanol.　Then,　alpha-Fe2O3　shell　was　produced　in　situ　on　the　surface　of　the　Fe3O4　nanoparticle　by　surface　oxidation　in　molten　salts,　forming　alpha-Fe2O3/Fe3O4　core-shell　nanostructure.　It　was　showed　that　the　magnetic　properties　transformed　from　ferromagnetism　to　superparamagnetism　after　the　primary　Fe3O4　nanoparticles　were　oxidized.　Furthermore,　the　obtained　alpha-Fe2O3/Fe3O4　core-shell　nanoparticles　were　used　to　photocatalyse　solution　of　methyl　orange,　and　the　results　revealed　that　alpha-Fe2O3/Fe3O4　nanoparticles　were　more　efficient　than　the　self-prepared　alpha-Fe2O3　nanoparticles.　At　the　same　time,　the　photocatalyzer　was　recyclable　by　applying　an　appropriate　magnetic　field.