In this paper, the structure and ielectric properties of BaO-TiO2 system ceramics were studied. By adding ZnO and Nb2O5 as sintering agents to the raw materials, the BaO-TiO2 system ceramics were sinteredat a temperature of 1260℃ for 2 hand have superior dielectric properties at 1 GHz: quality factor Q=12,500, relative dielectric constant "r37, temperature coefficient of dielectric constant "=0.30 ppm/℃. XRD pattern shows that the main crystal phase of the ceramics is Ba2Ti9O20, accompanied by a small number of additional phases: BaTi4O9, Ba4Ti13Zn7O34, Ba4Ti13O30 andTi 2Nb10O29, etc. The initial Ba/Ti ratio has a great effect on the dielectric properties of the ceramics, which can be explained by the variance in the formation of phases due to different Ba/Ti ratios.