Abstract: Aimed at the problem of large diameter Fresnel lens mold machining,this paper analyzed the large diameter Fresnel lens mold machining mechanism based on the ABAQUS finite element simulation software and modal test methods. The design and mold machining principle of Fresnel lens were introduced. Combined with the material constitutive relation and material failure criteria, a twodimensional 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 and feed on chip formation process.Resultsshow that the material strength and plastic brittle have significant impact on chip morphology in the H62 brass mold processing,the material strength is improved with the increase of strain rate,and the evolution process of the chip can be divided into: ribbon cuttings,serrated chips,and cell chips.