The electrical properties of Nb-doped SrTiO3 ceramics with and without excess TiO2 were investigated for anodes and interconnects of solid oxide fuel cells (SOFCs) by a DC 4-probe conductivity measurement. The microstructures and the grain boundary properties were revealed by SEM, EDX, SEM-EBSP-OIM and HRTEM. It was found that addition of excess TiO2 reduces the influence of the grain boundary on the conductivity of Nb-doped SrTiO3 ceramics, and the conductivity turned to be metallic in SOFCs operating temperatures The second phases such as TiO2 and Nb 2O5 were found in the composition of excess TiO 2. No grain boundary segregation was found, and randomly distributed grain boundaries were found predominant in the Nb-doped SrTiO3 ceramics with and without excess TiO2. The defects at the grain boundary were discussed.