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　a　special　fluid　that　can　be　made　flow　by　traveling　force　of　magnetic　field.　Therefore,　the　magnetic　fluid　is　suitable　for　using　as　the　working　fluid　of　flat　plate　heat　pipes　that　have　a　very　small　gap　between　evaporation　and　condensation　surfaces.　In　this　paper,　we　prepared　a　disk-shaped　wickless　flat　plate　heat　pipe,　and　the　distance　between　evaporation　and　condensation　surfaces　is　1　mm.　From　experimental　study,　the　effects　of　heat　flux　and　working　fluid　ratio　on　the　performance　of　the　flat　plate　heat　pipe　are　obtained　and　the　working　performance　of　the　magnetic　fluid　is　compared　with　that　of　the　water　flat　pate　heat　pipe　of　the　same　geometry　structure.