Nanoscratching-induced deformation in monocrystaline silicon is found to depend on the loading conditions. Molecular dynamics simulations reveal that amorphous phase transformation and nanotwins are the two major mechanisms. At a relatively low scratching depth, amorphous transformation occurs on the surface; however, when the scratching depth is greater than 1 nm, nanotwinning also emerges in the subsurface along 〈1 1 0〉 direction and its formation is associated with the body-centred-tetragonal-5 Si phase transformation. The twinning deformation stops at a Shockley partial dislocation.