Grinding fluids with different extreme pressure additives(sulfur,chlorine,phosphorus) were prepared.The effect of the extreme pressure additives on the GCr15 bearing steel surface roughness was analyzed through ultra high speed grinding test and using the surface roughness instrument and microscope,and the action mechanism of the extreme pressure additive in the grinding process was discussed.The results show that among the sulfur,chlorine,phosphorus extreme pressure additives,the grinding fluid containing sulfured fat oil and the grinding fluid containing chlorinated paraffin can obviously improve the grinding surface quality of GCr15 bearing steel,while the improvement of the grinding fluid containing phosphoric acid is not obvious.The grinding fluid containing sulfured fat oil posses the best lubricating effect,because the complex compound containing FeS or Fe2S3 which has good friction reducing and antiwear properties is formed by the chemical reaction of the active sulfur decomposed from the sulfured fat oil during the grinding process with the grinding metal surface.