In this work, high purity BaTiO3 (BT) nano-powders by a sol-gel process was prepared with Ba(NO3)2 and Ti(C4H9O)4 materials in order to acquire uniform size grains. The effects of the crystallinity, microstructure of BT nano-powders calcined at different temperatures and dielectric properties of the ceramics were investigated by XRD, SEM and impedance analyzer, respectively. Scanning electron microscopy and X-ray diffraction investigation revealed cubic plates and crystallite size. The results revealed that crystallite size and calcination temperature of BT and influence on the dielectric constant.