The chemical and electrical characteristics of the grain boundary of the polycrystalline semiconducting SrTiO3 ceramics, which were synthesized by hot-press sintering Na-coated semiconducting SrTiO3 powders, were investigated in terms of process parameters such as sintering temperature. Diffusion kinetic parameters such as diffusion coefficients and activation energy of diffusing ions at particular heat-treatment conditions were obtained by fitting experimental data with computer-simulated results as well as electrical features near the grain boundary of the ceramics.