The　effect　of　accelerated　flow　induced　by　pin　tip　clearance　on　fluid　flow　and　heat　transfer　characteristic　was　investigated　in　this　paper.　Three-dimensional　numerical　simulation　is　carried　out　with　adoption　of　Computational　Fluid　Dynamic　software.　The　steady,　laminar　flow　and　heat　transfer　equation　were　solved　by　using　a　finite-volume　method.　Analysis　results　show　that　influence　of　different　pin　tip　clearance　on　fluid　flow　and　heat　transfer　was　very　significant.　In　present　work,　the　optimal　non-dimensional　tip　clearance　(tip　clearance　divided　by　diameter)　respectively　were　0.3　and　0.5　with　the　condition　of　constant　flow　rate　and　pumping　power　consumption.