As a pore precursor, activated carbon of different contents (0 to 30 vol%) was added to (Ba,Sr)TiO3 powder. Porous (Ba,Sr)TiO3 ceramics were prepared by pressureless sintering at 1350 °C for 1 h in air. The effects of the activated carbon content on the microstructure and positive temperature coefficient of resistivity (PTCR) characteristics in porous (Ba,Sr)TiO3 ceramics were investigated. The porosity of the porous (Ba,Sr)TiO3 ceramics increased from 6.5% to 33.5%. The PTCR jump of the porous (Ba,Sr)TiO3 ceramics prepared with activated carbon was > 105and increased slightly with increasing activated carbon concentration. These results correspond to the Heywang model of the PTCR effect in (Ba,Sr)TiO3 ceramics, suggesting that activated carbon is an effective additive for preparing porous BaTiO3-based ceramics. The newly prepared (Ba,Sr)TiO3 ceramics can be used as a gas sensor.