The boiling heat transfer characteristics of refrigerant HFO-1234yf in a 7 mm O.D. micro-fin tube were investigated. The local heat transfer coefficients and pressure drops were measured at the mass fluxes of 100, 200, 400 kg/m(2) s, the heat fluxes of 4, 8, 12 kW/m(2), the saturation temperatures of 5, 15 degrees C and the oil concentrations of 0%, 1.5%, 3.0% and 5.0%. The influences of vapor quality, mass flux, heat flux and saturation temperature on the heat transfer coefficients were analyzed. The effect of lubricant oil on the boiling heat transfer performance of HFO-1234fy in the micro-fin tube was also discussed. All researches provided a good basis for the application of HFO-1234fy. (C) 2013 Elsevier Ltd. All rights reserved.