The dielectric properties of BaTiO₃ thin films and multilayers are different from bulk materials because of nanoscale dimensions, interfaces, and stress-strain conditions. In this study, BaTiO₃/SrTiO₃ multilayers deposited on SrTiO₃ substrates by pulsed laser deposition have been investigated by high-energy-resolution electron energy-loss spectroscopy. The fine structures in the spectra are discussed in terms of crystal-field splitting and the internal strain. The crystal-field splitting of the BaTiO₃ thin layer is found to be a little larger than that of bulk BaTiO₃, which has been interpreted by the presence of the internal strain induced by the misfit at the interface. This finding is consistent with the lattice parameters of the BaTiO₃ thin layer determined by the selected area diffraction pattern. The near-edge structure of the oxygen K edge in BaTiO₃ thin layers and in bulk BaTiO₃ are simulated by first-principle self-consistent full multiple-scattering calculations. The results of the simulations are in a good agreement with the experimental results. Moreover, the aggregation of oxygen vacancies at the rough BaTiO₃/SrTiO₃ interface is indicated by the increased [Ti]/[O] element ratio, which dominates the difference of dielectric properties between BaTiO₃ layer and bulk materials.