Abstract: Due to hybrid nanofluids having better thermophysical properties than fluid single nanoparticle, the cutting properties of 45 steel were studied with pure Al₂O₃, pure SiO₂ and different mass ratio of nanofluids for minimum quantity lubrication (MQL) milling. The results showed that hybrid nanofluids had lower milling force, contact angle and better micromorphology than pure SiO₂. However, hybrid nanofluids with different ratios of nanoparticles showed different lubrication effects. When the ratio of Al₂O₃ was less than that of SiO₂, SiO₂ were not completely covered by Al₂O₃ nanoparticles, so the lubrication effect was bad. With the increase of Al₂O₃’ proportion, the cutting force and contact angle were significantly reduced, and the surface quality of the workpiece was improved. When the mass ratio of Al₂O₃∶SiO₂ was 3∶1, the milling force, surface roughness and contact angle were the smallest, and the workpiece surface quality was the best. It could be seen that the content of Al₂O₃ affected the lubrication effect of hybrid nanofluids.