Molecular dynamics is used to simulate the deposition process of MgO molecules on MgO（001） surface，and substrate temperature and molecular incident energy are discussed in terms of their effects on the diffusivity of MgO molecules and the substrate surface coverage ratio. The simulated results show that with the substrate temperature increasing， vacant sites in MgO film decrease, owing to the increase in diffusivity of the deposited molecules on the substrate. At low temperatures， the substrate surface coverage ratio increases with molecular incident energy increasing. At high temperatures， the surface coverage ratio reaches the maximum at an incident energy of 3.0 eV， and then it decreases with the increase of incident energy.