Thin films of Sr1-xBaxBi4Ti4O15 (SBBT, x=0, 0.2, 0.4, 0.5, 0.6, 0.8, 1.0) with gradients in composition were prepared on silicon(100) substrate by a modified sol-gel technique using the salts of Sr, Ba, Bi and TiO2 as sources. Two types of graded thin films were designed. A special heating treatment procedure was employed in this study to form the uniform composition gradients at the temperature below 850degreesC. The results of Auger depth profiling indicate that the special process produces smooth and linear composition gradients. X-ray diffraction study clearly shows the formation of the Bi-based layered structure. Some of the peaks of the SrBi4Ti4O15, BaBi4Ti4O15 and the graded SBBT thin films were analyzed, as well as the relationship between the microstructural evolution of graded thin films and annealing conditions.