Formation and structure of gold nanoparticles at room temperature on the surface of carbon nanotube have been studied by molecular dynamics simulation.It was shown that，different from isolated gold nanoparticles，a gold nanoparticle AuN sitting on the surface of carbon nanotube undergoes a structural transition.Small gold nanoparticles with N≤130 have disordered structures while larger particles with N≥140 have the face centered cubic structure of bulk crystalline gold.The binding energy per atom of AuN decreases as its size decreases.It was also shown that the strength of the interaction between a small gold nanoparticle and the carbon nanotube is proportional to their contact surface area，indicating a close contact between the two structures.