Full atomistic molecular dynamics simulations have been used to study the diffusion of alkane molecule in single wall carbon nanotube (SWCNT), with. different alkane chain lengths and nanotube diameters. In this paper, we calculated the self-diffusion coefficient, mean-square gyration and bond-orientation order parameter of alkane molecule and the average intermolecular interaction energy per segment between SWCNT and alkane. Furthermore, structure of alkane in SWCNT was characterized through the radial distribution function, with results showing that the self-diffusion coefficient is related to the nanotube diameter. The component of mean-square gyration in z-direction scales with alkane chain length in SWCNT(9,9) like N-1.07 +/- 0.04, which is in good agreement with the prediction from scaling theory for polymers. The obtained results show that nanotube diameter and alkane chain length are important factors affecting the behavior of one-dimensional confined alkanes. (c) 2006 Elsevier Ltd. All rights reserved.