Sm0.1Ce0.9O1.95 (SDC) films, as promising electrolyte materials, have been successfully prepared on Al2O3 ceramic substrates by RF magnetron sputtering growth. The relationship between sputtering parameters and film microstructure was discussed. Scanning electron microscopy (SEM) and x-ray diffraction (XRD) were used to characterize the morphology and crystal structure of the SDC films. The SEM images show that the crystallinity becomes better and better with the increase of sputtering power from 100W to 300W. X-ray diffraction patterns indicate that the thin SDC electrolyte film on the Al2O3 ceramic substrate grows preferentially along the (111) compact plane with a pure fluorite structure when the RF power reaches 300W. After annealing treatment at 600°C and 800°C, respectively, it can be seen that SDC film becomes denser with few pinholes at the annealing temperature of 800°C. High oxygen ion conductivity (1.46×10-2 Scm-1) of the SDC film was obtained when the RF sputtering power and annealing temperature were 300W and 800°C, respectively.