The　vortex　tube　is　a　simple　device,　which　can　cause　energy　separation.　Although　it　has　a　very　simple　structure　and　is　operated　easily,　the　mechanism　in　it　is　very　complex.　The　performances　of　energy　separation　were　experimentally　studied　in　vortex　tubes　with　compressed　air　as　the　working　medium　and　the　relations　among　cooling　effect,　heating　effect,　inlet　pressure　and　cold　mass　flow　fraction　of　vortex　tube　were　obtained.　The　results　suggested　that　when　the　cold　mass　flow　fraction　is　less　than　85%,　the　higher　the　inlet　pressure　is,　the　better　the　cooling　effect　and　the　heating　effect　of　the　vortex　tube　with　the　nozzle　of　three　flow　passage　are.　The　less　the　cold　mass　flow　fraction　is,　the　better　the　heating　effect　is,　but　the　worse　the　cooling　effect　is.