The Al2O3 nano-films of different thicknesses (1~100nm) were successfully deposited on the monocrystalline Si surface by using ion beam sputtering deposition. The surface topography and the component of nano-films with different thickness were analyzed. The quality of the surface of nano-films was systematically studied. When the films’ thickness increase, the studies by atomic force microscope (AFM), X-ray photoelectron spectrum(XPS) show that the gathering grain continually grows up and transits from acerose cellula by two-dimensional growth to globularity by three-dimensional growth. The elements O, Al and Si were found on the surface of Al2O3 nano-films. With the thickness of the films increasing, the content of Al gradually increases and the intensity peak of Si wears off, the surface quality of the deposited films is ceaselessly improved