Abstract: The effect of B site substitution of Zr4+ for Ti4+ on microstructure and dielectric properties of Ba6-3xLa8+2xTi18O54(x=2/3)ceramics was investigated by solid-state reaction method.The results show that Zr4+ B site substitution for Ti4+ increased the sintering temperature of Ba6-3xLa8+2xTi18O54(x=2/3)ceramics from 1 350 ℃ to 1 600 ℃.A single-phase solid solution with like-perovskite tungsten bronze type structure was formed as the Zr4+ substitution for Ti4+ within a certain range,and the maximum solubility of Zr4+ was no more than 0.20.As the Zr4+ solubility exceeded 0.2,a second phase of Ba2ZrO4 was detected.With small Zr4+ substitution for Ti4+ in Ba6-3xLa8+2x(Ti1-zZrz)18O54(x=2/3)ceramics,a significant improvement of Qf value was achieved,the temperature coefficient of resonant frequency (τf)was slightly improved and the dielectric constant decreased.When intermingled quantity of Zr4+ was 0.05,the optimal microwave dielectric characteristics of the ceramics εr=86.83,Qf=5 875 GHz and τf=81.99×10-6/℃,were achieved after sintering at 1 400 ℃ for 2 h.