When Y2O3 was added to Ti-excess BaTiO3 ((Ba+Y)/Ti =1), the the area occupied by Y3+ ion was confirmed by its microstructure development, electrical conductivity behavior and lattice constant. Grain growth inhibition was observed when the content of donor dopant exceeded a critical value (x≈0.01) in BaTiO3+x(0.5Y2O3+TiO2) system. A donor-doped behavior was observed at various Y contents (0.2~3.0 mol% Y) when Y2O3 was added to TiO2-excess BaTiO3. As Y content was increased, (002) and (200) peaks shifted to higher angles and the lattice constant (a and c axis) decreased gradually. These results confirms that Y3+ ions preferentially occupy Ba sites when Ba/Ti < 1.