Abstract: The samples of U75V 60 kg/m heavy rail were heated to 900°C, simulating the temperature of heavy rail at the outlet of universal rolling, then the samples were cooled in open air for 25 s, simulating the temperature drop of heavy rail from the outlet to cooling bed; at last, the samples were put into air spraying channel to cool slackly on the top and both sides of rail head. The optimal cooling parameters were obtained after a lot of experiments: the distance between spraying nozzles and surface of rail head is 15 mm, the air pressure is 0.26 MPa, the spraying time is 80 s, and the air temperature is 28°C. Under this cooling condition, the hardened layer shows as "cap-shaped", the thickness of hardened layer at the center of rail head is more than 24 mm; the microstructure is fine pearlite, the average pearlite interlamellar spacing reduces about 50 nm than that before slack cooling; the tensile strength is more than 1300 MPa at the top fillets and the percentage elongation is more than 13%, increasing more than 20% and 60% than that before slack cooling, respectively.