This paper investigated resistivity and dielectric properties of magnesium doped BaTiO3. Influence of variable doping concentration and Ba/Ti ratio on densification, microstructure, resistivity and dielectric properties was studied. Ceramics sintered in pure nitrogen had higher apparent density than that of ceramics sintered in air. Second phase occurred when Mg doping concentration was greater than 2 mol%. Ceramics sintered in pure nitrogen had higher resistivity than ceramics sintered in air when A/B ratio ≥1. When Ba/Ti ratio was equal to 1.01, resistivity of the samples sintered in pure nitrogen increased with doping concentration increasing. Dielectric constant changed little with doping concentration increasing, but leakage conductivity decreased much. Samples with Ba/Ti ratio of 1.005 had the largest dielectric constant irrespective of doping concentration.