Bismuth silicate (Bi 4 Si 3 O 12 , BSO) nanostructured films containing 0, 1, 2, and 3 mol% Sr were prepared via sol-gel method and annealed at different temperatures up to 700°C. The effects of Sr content on the structure and morphology of prepared films were investigated. SEM images showed that surfaces of the prepared films were dense, smooth and homogeneous. The average particle size was changed from 30 to 35 nm as the annealing temperature was increased from 500 to 700°C. Variation of the dielectric constant and dielectric loss as a function of frequency and annealing temperature for the synthesized thin films with different content of Sr were also studied. The dielectric constant and dielectric loss decrease with Sr addition, and reach the minimum for the sample containing 2 mol% Sr. These changes could be attributed to the crystal structure and formation of secondary phases.