PMN ceramics with excess MgO addition in the range of 0 to 70m/o were prepared, and their electrical properties, such as dielectric constant, tan$delta$, diffuseness coefficient, remanent polarization, coercive field and electrical conductivity were measured. Dielectric constant and remanent polarization increased with up to 5m/o excess MgO and then decreased presumely due to the precipitation of second phase, etc. Electrical conductivity slightly increased with the addition of excess MgO.