An　effective　thermal　spreader　can　achieve　uniform　heat　flux　distribution　and　thus　enhance　heat　dissipation　of　heat　sinks.　Flat　plate　heat　pipe　is　one　of　the　highly　effective　thermal　spreaders.　Magnetic　fluid　is　liquid　and　can　be　moved　by　the　force　of　magnetic　field.　Therefore,　the　magnetic　fluid　is　suitable　to　be　used　as　the　working　fluid　of　flat　plate　heat　pipes　which　have　a　very　small　gap　between　evaporation　and　condensation　surfaces.　We　prepared　a　disk-shaped　wickless　flat　plate　heat　pipe,　and　the　distance　between　evaporation　and　condensation　surfaces　is　only　1　mm.　From　experimental　study,　the　effect　of　heat　flux　and　working　fluid　ratio　on　the　performance　of　flat　plate　heat　pipe　is　presented.　Also　we　compared　the　experimental　results　between　the　performance　of　water　and　magnetic　fluid　as　working　fluids.　(C)　2009　Elsevier　Inc.　All　rights　reserved.