The surface planarity and asperity removal behavior on atomic scale in an ultrathin water environment were studied for a nanoscale process by molecular dynamics simulation. Monolayer atomic removal is achieved under both noncontact and monoatomic layer contact conditions with different water film thicknesses. The newly formed surface is relatively smooth without deformed layers, and no plastic defects are present in the subsurface. The nanoscale processing is governed by the interatomic adhering action during which the water film transmits the loading forces to the Cu surface and thereby results in the migration and removal of the surface atoms. When the scratching depth ≥ 0.5 nm, the abrasive particle squeezes out the water film from the scratching region and scratches the Cu surface directly. This leads to the formation of trenches and ridges, accumulation of chips ahead of the particles, and generation of dislocations within the Cu substrate. This process is mainly governed by the plowing action, leading to the deterioration of the surface quality. This study makes the "0 nm planarity, 0 residual defects, and 0 polishing pressure" in a nanoscale process more achievable and is helpful in understanding the nanoscale removal of materials for developing an ultra-precision manufacture technology.