The microwave dielectric properties and the microstructures of MgNb 2 O 6 ceramics with CuO additions (1-4wt.%) prepared with conventional solid-state route have been investigated. The sintered samples exhibit excellent microwave dielectric properties, which depend upon the liquid phase and the sintering temperature. It is found that MgNb 2 O 6 ceramics can be sintered at 1140 o C due to the liquid phase effect of CuO addition. At 1170 o C, MgNb 2 O 6 ceramics with 2wt.% CuO addition possesses a dielectric constant ( r ) of 19.9, a Qxf value of 110,000 (at 10GHz) and a temperature coefficient of resonant frequency (τ f ) of -44ppm/ o C. The CuO-doped MgNb 2 O 6 ceramics can find applications in microwave devices requiring low sintering temperature.