The effects of B 2O 3 vapor on the sintering and the PTCR effect of BaTiO 3-based ceramics are investigated in this study. It is revealed that B 2O 3 vapor can be doped into both pure and Y-doped BaTiO 3 ceramics during sintering. B 2O 3 vapor not only obviously influences the densification and the grain growth but also increases the grain lattice parameters. The PTCR effect is improved through the doping of B 2O 3 vapor as the room temperature resistivity is considerably decreased and the resistance jump is greatly increased. With the doping of 1 mol% B 2O 3 vapor, semiconducting Y-BaTiO 3 with the room temperature resistivity of 30 Ω cm is obtained when the ceramics are sintered at as low as 1150 °C; while when the ceramics are sintered at 1350 °C with the doping of 0.25 mol% B 2O 3 vapor, the PTCR effect is enhanced by nearly two orders of magnitude and the room temperature resistivity is decreased from 25 to 9 Ω cm.