The　tribological　properties　of　PEEK　composites　filled　with　CaCO3　whisker　in　various　content　of　0-30%(weight　percent)　were　investigated.The　composite　specimens　were　prepared　by　compression　molding.　Tribological　testing　of　composites　in　water　lubrication　against　carbon　steel　ring　was　carried　out　on　a　MM200　block-on-ring　apparatus.Data　on　neat　PEEK　were　also　included　for　comparison.　The　morphologies　of　wear　traces　were　observed　by　SEM.It　was　observed　that　inclusion　of　CaCO3　whisker　significantly　improved　the　wear　resistance　and　reduced　the　friction　coefficient　of　PEEK　composites　under　water　lubricated　condition.　With　an　increase　in　CaCO3　whisker　contents,　the　specific　wear　rate　of　composites　decreased　and　showed　minima　for　20%　CaCO　3　content　as　5.2%　of　that　for　PEEK.　In　terms　of　friction　applications　under　water　lubrication,　the　optimal　content　of　CaCO3　whisker　in　PEEK　composites　should　be　recommended　as　15%　to　20%.The　SEM　observation　of　the　wear　traces　indicated　that　the　transfer　film　is　not　the　main　reason　for　the　enhancement　of　wear　resistance　of　the　composites　in　water　lubrication.CaCO　3　whisker　contributed　to　increase　the　load-carrying　capacity　and　abate　the　scuffing　and　adhesion　of　PEEK　composites,　finally　led　to　a　significant　improvement　of　the　wear　resistance.　©　(2010)　Trans　Tech　Publications.