We report the structural characteristics and the chemical bonding states of nano-sized BaTiO3 powders before and after having been heat treatment. We prepare BaTiO3 nanopowders by using the solvothermal method at different reaction temperatures. We anneal the prepared powders at 400 and 600 °C, respectively, for 1 h. We examine the structures of the prepared powders by using the Rietveld analysis, and the chemical bonding states of the ions by using a fitting program with an assumption that the measured spectra are Gaussian. Then, we study the morphology of the nanopowders, and measure the ferroelectric properties with frequency and reaction temperature. We show that the BaTiO3 nanopowders prepared by using the solvothermal method at lower reaction temperature exhibit the tetragonality and are useful for the electronic device applications.