Abstract: Wire drawing process is developing towards precision, high speed, low consumption and high production efficiency. Diamond coated drawing die is one of the most popular products. On the basis of summarizing the drawing die method of diamond coating prepared by direct current arc plasma jet technology, the coating quality is tested by Rockwell hardness tester, surface roughness profilometer, Raman spectrometer and optical microscope. The results show that the purity and the thickness uniformity of diamond coatings are both good. There are no serious cracks or film shedding at the edge of indented area under 1 470 N load. The average surface roughness R_a is 18 nm.