The material of alloy steel 40CrNiMoA's micro-milling process was simulated using the finite element method, with is built up with the Johnson-Cook coupled thermo-mechanical model , shear failure principle and Modified Coulomb friction law.. The distributions of the Mises stress, logarithmic strain, equivalent plastic strain and strain rate were obtained through finite element analysis. Meanwhile, the material's stress-strain curves of cutting deformation zones, formed surfaces, cutting chips and nearby cutting edge were given. These curves are very different from those stress-strain curves when the material is only stretched. There is no partial deformation stage on the curves of the first deformation zone, and there exists fierce indented fluctuation on the curves of deformation zone and the chip partial deformation stage. There are still exist some stress and strain no matter cutting chips or formed surfaces have reached stable.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.