Carbon chain inserted carbon nanotubes (CNTs) have been experimentally proven having undergone pronounced property change in terms of electrical conductivity compared with pure CNTs. This paper simulates the geometry of carbon chain inserted CNTs and analyzes the mechanism for conductivity change after insertion of carbon chain. The geometric simu-lation of Pt doped CNT was also implemented for comparison with the inserted one. The results indicate that both modification by Pt atom on the surface of CNT and addition of carbon chain in the channel of the tube are effective methods for transforming the electri-cal properties of the CNT, leading to the redistribution of electron and thereby causing the conductivity change in obtained configurations. All the calculations were obtained based on density functional theory method.