Cemented carbide is a kind of hard to process material with high hardness， strength， wear resistance and corrosion resistance. In order to achieve efficient and precise cutting of hard alloy materials， this paper takes polycrystalline diamond （PCD） tool milling of WC-15Co hard alloy as the research object. Based on the Bifano cutting thickness model， the critical cutting thickness of WC-15Co is calculated， and then compared with the maximum cutting thickness corresponding to the cutting parameters. The range of cross-domain milling parameters for the coexistence of brittle-domain cutting and ductile-domain cutting of the processed material is preliminarily determined. On this basis， through high-speed milling experiments， the effects of cutting parameters such as feed rate per tooth， radial cutting depth， and cutting speed on the machined surface quality and cutting force of the specimen are analyzed， and the mechanisms are explored. The results show that under the cross-domain milling parameters， that is， when the cutting speed is 300 m/min， the cutting rate per tooth is controlled within 11 μm/z and the radial cutting depth is less than 1 mm. The cutting surface in the ductile-domain can be obtained， the surface roughness is less than 0.2 μm， and there is no obvious brittle damage defect on the surface.The highest material removal rate can reach 157 mm³/min， significantly higher than that of the 43 mm³/min during the pure ductile-domain cutting.