Abstract: High-speed dry face-milling experiments on ultra high strength alloy steel, a kind of difficult-to-cut materials, with σ<SUB<b</SUB<<1.6 GPa, hardness 50HRc, were conducted using （Ti,Al）N coated carbide tools at the cutting speed range of 118～236 m/min. By the use of SEM and energy spectrometer, and taking tool life as a criterion for a comparative evaluation of the tool's cutting performance, the wear mode and mechanisms of rake face and flank face wear, coupled with the cutting performances of carbide tools are discussed. Experiments indicate that under the conditions of high-speed cutting, the primary wear mechanisms of （Ti,Al）N coated carbide tools are adhesion, diffusion and chemical wear; the wearing modes are the rake face craters, accompanied by the peeling off the coating to expose carbide substrate in the rake face and the chippings of cutting edges.