The high dielectric constant X8R dielectric materials could be sintered at 1,240 °C by doping 2.5 mol% Pb(Ti,Sn)O3 additives into the BaTiO3 ceramics, with a dielectric constant greater than 3,400 at 25 °C, dielectric loss lower than 2.0% and temperature coefficient of capacitance (TCC) less than ±15% from −55 to 150 °C, which satisfied X8R specification. The effects of Pb(Ti,Sn)O3 on the microstructure and dielectric properties of BaTiO3-based ceramics were investigated. Doped with Pb(Ti,Sn)O3 additives, the partial solid solution was formed between Pb(Ti,Sn)O3 and BaTiO3. Due to the high Curie point of Pb(Ti,Sn)O3, the Curie point of the ceramics was markedly shifted to higher temperature about 150 °C, and the temperature coefficient of capacitance curves was flattened. The increase of the tetragonality (c/a ratio) and the fine microstructure were resulted in the increase of dielectric constant. With Pb(Ti, Sn)O3 content up to 3 mol%, the depression of Ti4+’s polarization and the decrease of the tetragonality (c/a ratio) were resulted in the decrease of dielectric constant.