Today, many machining processes are conducted with cutting fluids, which are used for cooling the workpiece, the tool and the machine during cutting. Furthermore, the friction process is reduced and the created chips are removed from the cutting area. Unfortunately, coolants create high coats in production and can be hazardous to the environment and human health. Increasing environmental pollution and problems concerning waste disposal demand the development of ecological manufacturing technologies. Today"s research activities are concentrated on improving the properties of cutting tools for dry machining by optimizing manufacturing technologies and tool geometries, by alloying of special cutting materials and by coating of tools. In this paper, two coating of tools(C3N4-film, diamond film)are studied, main study work include the following two parts:1. The diamond film coating tools used in dry-cutting.The diamond films coating has as high hardness, high wear resistance, low friction coefficient and high thermal conductivity as the natural diamond. The diamond films coated tools are used for turning, especially for modern high speed dry cutting, the productivity of cutting Si-Al alloy can be greatly improved by using cutter coated with diamond film in high speed dry cutting. In this paper, the dry-cutting tests were carried out by diamond film coated tool on Si-Al alloy and this tool s cutting properties were studied. The results indicate that the wearing process of diamond-film-coated cutter is from the micro-cracking of the film at the beginning to the gradual dropping in the end; The main effective factor of surface roughness is feed, the paper establishes the mathematical model of surface roughness through a large number of cutting experiments. 2. The C3N4 films coating tools used in dry-cutting.C3N4 is a new kind of superhard material and has comparable properties with diamond in high hardness, wear-resistance, low friction coefficient and thermal conductivity. In this paper, the DC magnetic sputtered film method was used to deposit C3N4 film on cemented carbide (YT15), the micro-hardness Hv=72.04Gpa,adhersive force was qualified the standard of JB/T8365-96. This cutting tool was tested in dry-cutting area, and its cutting properties were studied to machine quenched steel. The cutting experiments show that in cutting of quenched steel the tool life of this cutter is longer than that of uncoated cutting tool.