The invention relates to an air cooling mechanism for a screw rod, and is mainly used in a high-precision machine tool. No cooling mechanism which has a simple structure and a good cooling effect on the screw rod exists currently. The air cooling mechanism for the screw rod is characterized by consisting of an inner ring, an outer ring and a plurality of screws, wherein the inner ring consists of an inner ring body and an air cooling sleeve, an inner ring circular hole is arranged in the inner ring body, a screw rod channel is arranged in the air cooling sleeve, a wall surface of the air cooling sleeve is uniformly provided with two circles of air outlet holes, and axes of the air outlet holes are all vertically intersected with the axis of the air cooling sleeve; and the air cooling sleeve is fixed on the inner ring body, the outer ring consists of an outer ring body and an outer ring loop, an outer ring circular hole is arranged in the outer ring body, a wall surface of the outer ring loop is provided with an air inlet, the inner ring and the outer ring are fixed through the plurality of screws, the screw rod channel is aligned to the outer ring circular hole, and the inner ring body, the air cooling sleeve, the outer ring body and the outer ring loop define a cooled air distribution cavity in an annular structure. The air cooling mechanism has a simple structure, is low in manufacturing cost, and has a good cooling effect on the screw rod.