The　present　work　aims　to　study　the　influence　of　Fe3O4-water　nanofluids　on　capillary　performance　in　microgrooves　wick　for　guiding　the　promotion　of　thermal　performance　of　two-phase　heat　transfer　devices.　Capillary-rise　experiment　was　conducted　to　measure　the　capillary　performance　at　different　temperatures.　Contact　angle　and　permeability　were　derived　from　the　result　of　the　experiment　to　evaluate　the　wetting　and　the　flow　in　the　groove.　It　was　found　that　the　nanofluids　significantly　enhanced　capillary　performance　in　the　wick　with　improving　the　wetting　and　the　flow.　Depending　on　the　temperature　and　particle　concentration,　Capillary　Performance　Parameter　was　increased　by　875%　in　comparison　to　that　for　the　base　liquid.　There　exists　an　optimal　concentration　at　which　the　decrease　of　the　contact　angle　and　the　increase　of　the　permeability　achieve　the　maximum.　Raising　the　temperatures　of　the　fluid　and　the　wick　facilitated　the　nanofluids　to　improve　the　wetting　but　diminished　the　friction　reduction.　The　fundamental　mechanism　is　analyzed　based　on　the　discussions　of　the　roles　of　particle　migrations　existing　in　the　cross-section　of　the　groove　and　particle　aggregation.　©　2020　Elsevier　Ltd