The dielectric properties of BaTiO3 ceramics having abnormally grown grains were investigated. When BaTiO3 were doped by 0-5 mol% of CuO, CuO0.5 CuTi0.33O1.33 and sintered at 1000-130$0^{circ}C$ the abnormal grain growth accelerated as the Cu content or the sintering temperature increased. As area fractions of abnormal grown grains increased the amount of tetragonal phase increased. Also the relative dielectric constant ($varepsilon$r) at room temperature decreased maximum $varepsilon$r at Tc decreased and hence sharper phase transformation occurred at Tc as area fractions of abnormal grown grains increased. The results were interpreted as a process of internal stress relaxation resulting from the increase of 90$^{circ}$ domains induced bythe increase of area fractions of abnormally grown grains