The self-diffusion model of Lennard-Jones fluid confined in a nanoscale space is developed by using equilibrium molecular dynamics simulation. The radial distribution function in free and confined space is evaluated and compared to analyze the fluid microstructure. The effects of the confined scale, strength of the fluid-solid coupling and commensurability of wall and fluid density on the fluid self-diffusion are investigated and discussed. The results indicate that the confined scale, fluid-solid coupling strength and commensurability of wall and fluid density play considerable role in the self-diffusion coefficient for the fluid confined in nanoscale space. Decrease in the confined scale lead to large portion of fluid molecules 'feel' the wall interaction, which results in the reduction of self-diffusion coefficient. In addition, the reduction of fluid self-diffusion coefficient in confined space is also demonstrated when the wall and fluid densities are incommensurate and wall-fluid coupling strength is large. (C) 2011 Elsevier Ltd. All rights reserved.