Abstract: It is especially important to achieve the material removal mechanism during nanoscale machining to realize ultra-precision machining of single crystal nickel. Therefore, the mechanical and thermal behavior, surface/subsurface formation characteristics and plastic deformation mechanism of single crystal nickel nanocutting were studied by molecular dynamics simulation to reveal the material removal mechanism. The results showed that the ordered nickel atoms were removed as amorphous structure by tool extrusion and shear during nano-cutting of single crystal nickel. Some of the nickel atoms with FCC structure were transformed into HCP structure and amorphous structure, dominating the phase transition and amorphization. Meanwhile, there appeared dislocation of 1/6<112>, 1/3<100>, 1/6<110>, 1/3<111> and 1/2<110> of the Bergdahl vectors appeared, respectively. The plastic deformation mechanisms were phase transition, amorphization and dislocation slip during nano-cutting of single crystal nickel. A dislocation reaction in which 1/2<110> perfect dislocations were transformed into 1/6<112> partial dislocations occurred due to the fact that the geometrical and energetic conditions were satisfied simultaneously during nano-cutting. The defect structures including dislocation ring, stair-rod dislocation, prismatic dislocation, V-shaped dislocation, atomic cluster and vacancy were observed on the machined subsurface under the action of cutting force-heat. The cutting along the (111) crystal plane was favorable to reduce the depth of the subsurface defect layer compared with the (100) crystal plane and the (110) crystal plane.