Abstract: The effect of some process parameters,such as solution concentration,spin speed,volatility and vapor absorbing ability of solvents,on the qualities of the spin coated polymer thin films on silicon substrate is discussed.An experiential equations was summarized to describe the relationship between the thickness of the PS films and the solution concentration and spin speed.Possible conditions that may lead to fault on films are analyzed,and some characters of the film such as the thickness,infra-red absorbing spectrum and topography are tested.