Strontium　hexaferrite　(SrFe12O19)　nanoparticles　were　prepared　using　ethylene　glycol　(EG)　assisted　hydrothermal　synthesis.　The　experimental　results　revealed　that　the　reaction　temperature　and　the　amount　of　EG　had　an　effect　on　the　size,　morphology　and　magnetic　properties　of　SrFe12O19　nanoparticles.　SrFe12O19　nanoparticles　with　a　size　of　about　25　nm　were　obtained　at　140　degrees　C　for　24　h　at　the　EG/W　volumetric　ratios　of　1/1.　The　saturation　magnetization　of　the　particles　was　approximately　10.6　emu/g.　Furthermore,　SrFe12O19　nanoparticles　modified　by　oleic　acid　could　be　dispersed　in　high　boiling　point　mineral　oil　to　form　highly-concentrated　magnetic　fluid.　The　magnetic　and　rheological　properties　of　magnetic　fluid　were　investigated　using　a　Gouy　magnetic　balance　and　a　rotational　rheometer,　respectively.　The　magnetic　fluid　showed　excellent　stability　in　gravity　field　and　external　magnetic　field,　and　exhibited　shear-thinning　behavior.　Moreover,　the　magnetic　fluid　had　obvious　heating　effect　in　an　alternating　magnetic　field　and　had　potential　on　hyperthermia　therapy　of　tumor.　(C)　2013　Elsevier　B.　V.　All　rights　reserved.