The microstructures and the microwave dielectric properties of the (1−x)Mg 4 Nb 2 O 9 –xCaTiO 3 ceramic system were investigated. In order to achieve a temperature-stable material, CaTiO 3 (τ f ∼800ppm/°C) was chosen as a τ f compensator and added to Mg 4 Nb 2 O 9 (τ f ∼−70ppm/°C) to form a two phase system. It was confirmed by the XRD and EDX analysis. By appropriately adjusting the x-value in the (1−x)Mg 4 Nb 2 O 9 –xCaTiO 3 ceramic system, near-zero τ f value can be achieved. A new microwave dielectric material, 0.5Mg 4 Nb 2 O 9 –0.5CaTiO 3 applicable in microwave devices is suggested and possesses the dielectric properties of a dielectric constant ɛ r ∼24.8, a Q×f value ∼82,000GHz (measured at 9.1GHz) and a τ f value ∼−0.3ppm/°C.