In this paper, we have studied the formation of silicon nanoparticles on surfaces of carbon nanotubes by molecular dynamics simulation. We found that, due to the Si-nanotube interaction and the enormous curvatures of carbon nanotubes, Si atoms on the surface of a carbon nanotube prefer to form a three-dimensional nanoparticle rather than a thin film covering the nanotube.Small Si nanoparticles have similar atomic structures as are found in Si nanoparticles grown without any substrate.Large Si nanoparticles are elongated in the axial direction of the nanotube and have amorphous network structures of Si，different from the crystalline structure of Si nanoparticles without considering Si-nanotube interaction.