Effects of Ta substitution for Nb on the microwave dielectric properties of BiNbO 4 ceramics have been investigated. BiNb ( 1 - x ) Ta x O 4 (x=0, 0.1, 0.2, 0.3, 0.4) with 0.3 wt.% CuO-V 2 O 5 mixtures addition can be densified at very low sintering temperature below 860 o C. The dielectric constants ( r ) of the Ta-modified BiNbO 4 ceramics increase with increasing of Ta contents, but the Qxf values have no apparent changes. The temperature coefficient of resonant frequency (τ f ) changes from positive to negative with change of x values. The crystalline phase and microstructure of Ta-modified BiNbO 4 ceramics have been characterized by X-ray diffraction and scanning electron microscopy respectively.