The effect of Si3N4 addition on the microstructure and PTCR characteristics of BaTiO3 was studied. When 0.1 mol% Sb2O3-doped BaTiO3 codoped with Si3N4 (0.1, 0.25, 0.5, 0.75, and 1 wt%, respectively) were sintered, their microstructures were changed by the amount of the liquid phase as a result of eutectic reaction at 126$0^{circ}C$. By these microstructural changes, the specific resistivity ratio($ ho$max/$ ho$min) with Si3N4 content variation of 0.1 mol% Sb2O3-doped BaTiO3 ceramics sintered at 130$0^{circ}C$ for 1 hour varied between 3.70$ imes$102(0.1 wt% Si3N4) to 1.16$ imes$103 (1wt% Si3N4).