Nb-doped 0.8BaTiO3-0.2Bi(Mg0.5Ti0.5)O3 ceramics were prepared by conventional solid-state method. The dielectric properties and the structural properties were investigated. When Nb2O5 is doped into 0.8BT-0.2BMT system, a small amount of Ba4Ti12O27 secondary phase is formed. The lattice parameters gradually increase with the Nb2O5 doping. It is found that the temperature-capacitance characteristics greatly depend on Nb2O5 content. With the addition of 3.0 mol% Nb2O5, a 0.8BT-0.2BMT ceramic sample could satisfy the EIA X9R specification. This material is promising for high-temperature MLCC application.