This paper has investigated the impact of the substrate temperature and Ar ion assisted deposition on the surface structure formation mechanism and the film properties during the amorphous TiO2 thin film deposition process with the molecular dynamics simulationmethod. The results show that the reduction of the surface roughness happen when the energy of Ar ions assisted is increased or the substrate temperature rises, and also the film density on surface is changed with the increasing of Ar ions energy and substrate temperature. It is also found that the Volmer-Weber (island) growth mode of films is promoted by the lower Ar ion energy and higher substrate temperature when the substrate has an island structure. The assisted Ar ion has power of making a flat surface and increasing the local temperature. Besides, it will influence the growth mode with the change of surface atom mobility. With a high assisted Ar ion energy the Volmer-Weber (island) growth mode is inhibited, which will be conducive to the formation of more smooth film surface. (C) 2017 Elsevier B.V. All rights reserved.