Abstract: The cutting performance of C-doped TiAlSiN coating for high hardness materials was investigated.The microstructure of the coating was observed by scanning electron microscope, the elemental composition of the coating was characterized by EDS, the phase composition of the coating was analyzed by XRD, the surface roughness of the coating was characterized by three-dimensional morphology instrument, the hardness of the coating was evaluated by nano indentation instrument, and the thickness of the coating was measured by ball mill instrument.The cutting performance of high hardness die steel Cr12 was compared by cutting experiments with four-edge TiAlSiN and TiAlSiCN coating milling cutter.The tool wear was compared by milling the same distance, and the surface roughness of processed materials was measured by hand-held roughness meter.The effects of C doping on the cutting performance of TiAlSiN coating and the surface roughness of processed materials were analyzed.The results show that there are fewer droplets and pinholes on the surface of TiAlSiCN coating than that of TiAlSiN coating, and the hardness of TiAlSiN coating increases from 37.6 GPa to 46.3 GPa, when TiAlSiCN coating is doped with C.In the cutting test, when TiAlSiCN and TiAlSiN coated milling cutter cut the same distance, the edge wear of TiAlSiN coated milling cutter is more serious than that of TiAlSiCN coated milling cutter.The average roughness of TiAlSiN coated milling cutter cutting material surface is 0.046.The average roughness of TiAlSiCN coated milling cutter cutting material surface is 0.025, the workpiece surface roughness decreases by nearly 50%.C doping can not only improve the surface microstructure of TiAlSiN coating and reduce the roughness of the surface of the processed material, but also improve the hardness of the coating and prolong the service life of the milling cutter.