Barium titanate (BT) nanoparticles with different diameters were prepared by the Sol-Gel method. The diameter and lattice constant of nano particles were determined by XRD. We also measured the lattice vibration of BT nano particles by Raman scattering to discuss the size effect, and calculated the intrinsic dielectric constant of BT nano particles through the analysis of lattice vibration. Furthermore we confirmed the shift in Curie temperature by the size effect.