Effect of ZnO ratio on the phase formation, the microstructure and microwave dielectric properties of BaO–ZnO–TiO2 ceramics with compositions varying from 1:0.5:3 to 1:0.8:3 (BaO:ZnO:TiO2) were investigated. XRD patterns show that The bulk densities of the sintered samples were measured by the Archimedes method. The phase compositions were identified by X-ray diffraction (XRD) using Cu Kα radiation (DX-1000 CSC). Microstructure observation was conducted by using scanning electron microscopy (SEM, FEI Inspect F). The dielectric characteristics at microwave frequencies (4.726–4.953 GHz) were measured by the Hakki–Coleman dielectric resonator method in the TE011 mode using a network analyzer(HP83752A) [14]. The sintered samples used for this measurement had the ratio: diameter:height = 1.9–2.3. The τf values were determined from the difference between the resonant frequencies obtained at 25 °C and 80 °C.