In nano-machining, some alloys exhibit crystalline plastic deformation properties, while others exhibit amorphous deformation properties. However, the conversion mechanism between crystalline and amorphous properties is still unclear. In this paper, molecular dynamics (MD) simulation methods were employed to study the plastic deformation transformation mechanism between crystalline and amorphous during nano-machining of Cu-Al alloys. The simulation results show that Cu-Al alloys with different element ratios will complete amorphization as long as the proportion of FCC crystal structure in the alloy is less than 86%. Meanwhile, the material removal rate, ploughing width, and cutting force change significantly during the amorphization process. The lower the potential energy of the atoms inside the Cu-Al alloy, the higher the temperature required for amorphization. This work can enrich the understanding of the material removal mechanism of alloy material.