R1234yf　is　regarded　as　an　ideal　substitute　for　R134a　in　supercritical　organic　Rankine　cycles.　This　study　exper-imentally　analyzed　the　convective　heat　transfer　coefficients　of　supercritical　R1234yf　in　a　micro-fin　tube.　The　experiments　show　the　influence　of　the　system　operating　parameters　including　pressure,　heat　flux　and　mass　flux　on　the　heat　transfer.　Then,　this　paper　compares　the　heat　transfer　rates　for　R1234yf　and　R134a　at　supercritical　pressures　and　the　ability　of　existing　correlations　to　predict　the　heat　transfer　coefficients　with　R1234yf.　The　results　show　that　as　q/G　increases,　the　buoyancy　increases　Nubottom,　while　the　variations　in　Nutop　are　divided　into　two　regions　based　on　the　bulk　fluid　enthalpy.　The　influence　of　pressure　on　the　heat　transfer　is　also　related　to　the　bulk　fluid　enthalpy.　When　the　bulk　fluid　enthalpy　is　less　than　a　critical　value,　Nubottom　and　Nutop　both　increase　with　decreasing　pressure　and　then　decrease　above　this　critical　enthalpy.　The　heat　transfer　coefficient　is　no　longer　enhanced　at　the　top　with　large　buoyancy　forces.　For　low　mass　fluxes,　the　heat　transfer　coefficients　of　R134a　and　R1234yf　are　similar.　For　high　mass　fluxes,　the　heat　transfer　coefficients　of　R134a　are　higher　than　those　of　R1234yf.　The　Wang　correlation,　that　was　based　on　R134a　data,　more　accurately　predicts　the　heat　transfer　co-efficients　than　other　correlations　for　supercritical　R1234yf　in　the　horizontal　micro-fin　tube.　Among　all　the　4050　experimental　points,　90.17%　of　Nutop　and　84.49%　of　Nubottom　were　predicted　with　errors　of　less　than　30%　by　the　Wang　correlation.