Abstract: A Monte Carlo method was used to study the effects of nanotube diameter, structure and interaction between the nanotube and nickel on the structure of encapsulated nickel. Results show that the structure of the encapsulated nickel is dependent on the nanotube diameter and concentric layered structures, with and without a single atomic chain, alternate with increasing nanotube diameter. In addition, the structure of nanotube and the interaction between the metallic nickel and the nanotube have no obvious influence on the structure of encapsulated nickel.