Molecular dynamics simulation of nanoparticle colliding with monocrystalline silicon surface has been carried out in order to investigate the repulsion behavior of nanoparticles. The dynamical behavior of the nanoparticle, the atomistic structure of elastic and plastic deformation of the substrate, and the transformati on of energy during the collision process are analyzed. A hemispherical crater i s formed on the Si(001) substrate, and there exists an amorphous layer on the wa ll of the crater. In the collision process, the atoms of the substrate that lie near the nanoparticles transform to amorphoustate immediately. And the elastic d eformation which is characterized by the reversible (111)［110］ glide structure is produced outside the amorphous layer. During the incidence stage, the substr ate undergoes compressed elastic deformation. And during the repulsion stage, th e potential energy of the substrate declines oscillatory with compressed elastic deformation and tensed elastic deformation formed alternately. The compressed e lastic deformation energy stored in the substrate is transferred to the transnat ional kinetic energy of the nanoparticle, which forces it back from the surface.