This　paper　describes　the　analysis　of　the　chip　formation　mechanism　in　mold　machining　process　of　large　diameter　Fresnel　lens　based　on　the　ABAQUS　finite　element　simulation　software　and　modal　test　methods.　Combined　with　the　material　constitutive　relation　and　material　failure　criteria　etc,　a　two-dimensional　orthogonal　cutting　model　was　established　and　the　chip　derived　from　the　simulation　was　compared　with　the　chip　from　modal　test,　with　a　consequent　verification　of　the　feasibility　of　simulation　chip　model.　The　simulation　contributes　to　an　investigation　into　the　effects　of　the　cutting　speed　on　chip　formation　process.　The　results　show　that:　the　material　strength　and　plastic　brittle　have　significant　impact　on　chip　morphology　in　the　H62　brass　mold　processing,　and　material　strength　will　improve　with　the　increase　of　strain　rate,　the　evolution　process　of　the　chip　of　material　plastic　reduction　can　be　divided　into:　ribbon　cuttings,　serrated　chips,　cell　chips.　©　(2014)　Trans　Tech　Publications,　Switzerland.