Abstract: On the basis of DC arc plasma jet chemical vapor deposition of diamond,CVD diamond coatings were prepared on the inner surfaces of cemented carbide drawing dies with diameters ofΦ78.0 mm andΦ145.0 mm by using two different plasma torches and corresponding equipment and processes,and the surfaces of diamond coatings were polished.The roughness,thickness,composition and adhesion strength of the coating were tested and analyzed by 3D profiler,optical microscope,Raman spectrometer and pressure testing machine.The results show that the surface roughness of diamond coatings prepared by the two methods is 42.426 nm and 33.084 nm,respectively.The thickness uniformity and purity of diamond coating are good.Under the load of 1 000 N,there is no serious crack and film shedding in the edge area of indentation.The prepared drawing die is applied to the smooth aluminum sheath drawing production line of high voltage and ultra-high voltage cables,which can adopt one-time diameter reduction process,dry drawing at low speed or drawing with water lubrication at 3-5 m/s,and its service life is more than 10 times that of cemented carbide die.