This paper studied the cutting experiments of dry turning the cemented and hardened steel 20CrMnTi using cemented carbide cutting tools, ceramic cutting tools and PCBN cutting tools. Through measuring the value of surface roughness in varying cutting conditions, analyzed the influence of cutting speed and the feed rate to the surface roughness, obtained two empirical formulas Ra-v and Ra-f. This research results provided valuable cutting data for practical production, and verified cutting instead of grinding of dry cutting the cemented and hardened steel 20CrMnTi is feasible.