The half-dry cutting employs cryogenic compressed air cooled down to (10 to 40) u001f and a micro-dosage of lubricating oil, called cryogenic cold air jet cutting was studied. On the basis of a comparative experiment on dry and cryogenic cold air jet cuttings carried out for grade 45 steel, the effects of cryogenic cold air jet on the breaking of chips were discussed. The experimental results reveal that in the valid ranges of pressure and temperature, the cryogenic cold air jet widens the chip breaking areas effectively. When the cutting depth is not greater than 1 mm, the influence of chip breaking is much more significant. But different injecting angle of cold air has different influence on the chip-break. From the experiment, the optimized jet injecting angle, temperature effecting range and pressure working range of cold air are obtained. These results can offer a foundation for industrial manufacturing. The half-dry cutting employs cryogenic compressed air cooled down to (10 to 40) u001f and a micro-dosage of lubricating oil, called cryogenic cold air jet cutting was studied. On the basis of a comparative experiment on dry and cryogenic cold air The experimental results reveal that in the valid ranges of pressure and temperature, the cryogenic cold air jet widens the chip breaking areas effectively. When the cutting depth is not greater than 1 mm, the influence of chip breaking is much more significant. and pressure working range of cold air are obtained. These results can offer a foundation for industrial manufacturing.