In our previous studies, an investigation aiming at finding what affects the microstructure and density of BaTiO3 by spark-plasma-sintering (SPS) has been reported. However, in this paper, BaTiO3 with different grain size ranging from 80 nm to several micrometers are prepared by controlling SPS conditions and the relations between the grain size and dielectric properties have been studied. XRD and Raman spectroscopy analysis suggest tetragonality decreases with smaller grain size because the orthorhombic structure starts to present in the pellets. For quantifying the tetragonal content, the XRD profiles around 20 = 10-90degrees of BaTiO3 were analyzed according to Gaussian-Lorentzian distribution after the elimination of Kalpha(2) component and in a further step the tetragonal content in the pellets with different grain size were calculated. The temperature dependence of relative permittivity indicated that decreased tetragonal content can deteriorate the dielectric properties and T-c shifts to lower temperature with reduced grain size. The former can be attributed to the decreased area of the domain wall per volume with decreased tetragonal content while the latter can be interpreted as the internal stress produced from phase transformation. (C) 2003 Elsevier B.V. All rights reserved.