Grazing incidence x-ray diffraction has been employed to perform the depth-profile analysis on SrBi2Ta2O9 (SBT) thin films with different preferential orientations. For the polycrystalline SBT thin film, the change in structural orientation occurs only within the 15-nm-thick top layer, which is associated with the formation of the (200)-predominant SBT thin film prepared by the layer-by-layer annealing process. The inhomogeneity of structural orientation is more significant in the full film thickness for the (200)- predominant SBT thin film. (0010) peak can only be observed for the grazing angle larger than 0.6°. A layer with the highest ratio of I(200)/I(115) is found in the top surface layer (i.e., the latest layer during deposition) of the (200)-predominant SBT thin film.