The　work　aims　to　analyze　the　formation　process　and　mechanism　of　high-speed　milling　sawtooth　chip　in　aerospace　aluminum　alloy　so　as　to　provide　a　theoretical　basis　for　improving　the　surface　quality　of　the　workpiece　and　prolonging　the　service　life　of　the　tool.　By　considering　the　characteristics　of　milling　thickness　variation　during　high-speed　milling　of　aerospace　aluminum　alloys,　reasonable　constitutive　model　and　material　fracture　criterion　were　selected　to　simplify　the　3D　milling　as　2D　variable　thickness　orthogonal　cutting　thermal　coupled　finite　element　model　and　the　formation　process　of　sawtooth　chips　was　simulated　to　verify　the　accuracy　of　finite　element　model　through　milling　experiments.　The　milling　force,　milling　temperature　and　morphology　of　sawtooth　chip　were　accurately　predicted　within　the　cutting　speed　range　of　2~16　m/s.　As　the　cutting　speed　increased,　the　thickness　of　the　chip,　the　height　of　the　continuous　portion　and　the　shear　band　spacing　all　decreased.　On　the　contrary,　the　shear　angle　increased　as　the　cutting　speed　increased.　When　the　cutting　speed　was　16　m/s,　the　saw-toothed　chips　appeared　on　the　side　with　the　larger　chip　thickness,　and　gradually　disappeared　with　the　reduction　of　the　chip　thickness　and　then　became　uniform　strip-shaped　chips.　The　sawtooth　chip　was　accurately　simulated　under　the　change　of　cutting　thickness.　A　three-stage　sawtooth　chip　formation　model　considering　the　variation　of　the　shear　band　width　is　proposed.　The　adiabatic　shear　process　is　analyzed　by　the　changes　of　stress,　strain,　strain　rate　temperature　inside　and　outside　of　the　shear　band,　and　the　segmentation　intensity　ratio　parameter　is　used　to　quantify　the　degree　of　sawtooth　chip　strain　and　control　the　shape　of　the　sawtooth　chip.　©　2019,　Chongqing　Wujiu　Periodicals　Press.　All　rights　reserved.