The phase structure, microstructure and microwave dielectric properties of Ba([Mg1−xZnx]1/3Ta2/3)O3 (BMZT, 0 ≤ x ≤ 0.25) ceramics were researched as a function of ZnO addition by the traditional solid-state ceramic route. X-ray diffraction (XRD) analysis showed that there were two phases: main crystalline phase Ba(Mg1/3Ta2/3)O3 (BMT) and secondary phase Ba0.5TaO3. SEM photograph indicated that ZnO working as a sintering aid promoted the grain growth and densification. As increasing x from 0 to 0.25, the dielectric constant (er) increased continuously from 23.7 to 25.9, and the Q × f value initially increased from 62,300 GHz to the peak value of 158,900 GHz (x = 0.2) and declined to 96,500 GHz thereafter. Meanwhile, the temperature coefficient of resonant frequency (τf) initially declined to 0.15 ppm/°C (x = 0.2) and then increased to 2.9 ppm/°C. Ceramics with superior microwave dielectric properties: er = 25.7, Q × f = 158,900 GHz (f = 8 GHz) and τf = 0.15 ppm/°C were obtained at x = 0.2.