The effects of two rare earth oxides such as CeO2 and Sm2O3 on the phase structure and dielectric properties of BaTiO3 ceramic were investigated. Results indicate that the dielectric constant of this system will increase greatly with the increasing content of these two oxides, and Ce4+ substitutes for Ba2+ located at A-site in ABO3 structure. Quantitative XRD analysis shows that c/a ratio in the sample with addition of CeO2 will increase, which implies the increase of tetragonality in system, causing the augment of dielectric constant, and the decrease of the crystal’s geometrical symmetry results in curie-temperature moving towards low temperature; Sm3+(0.096 nm) substitutes for Ba2+(0.135 nm) possessing larger radius in A-site and the electrovalency in A-site increases, the mutual effect is strengthened, so the polarization is enhanced, and the dielectric constant increases notablely.