X-ray reflectivity and grazing incidence crystal truncation rod (CTR) measurements were employed to characterize the microstructure and crystallization behavior of homoepitaxial SrTiO3 (STO) films deposited on polished SrTiO3 (0 0 1) substrates by pulse laser deposition technique. X-ray scattering results indicate that room temperature grown STO film has a density approximately 11.1% lower than that of bulk STO and shows poor epitaxial relation with the substrate. Subsequent annealing at 760 degreesC for 20 s appeared to transform the film into two-layer structure, with the density of the layer right above the substrate approaching to its bulk value, while the density of the top 15.5 Angstrom thick layer reducing to near 45% of bulk STO. The annealing process also leads to an increase of lateral lattice constant together with the growth of domain size. The appearance of interference fringes of the CTR after annealing, which is also observed at the film grown at 760 degreesC, clearly demonstrates the development of epitaxy upon short time annealing.