In this study, the microwave dielectric properties of La2.98/3Ba0.01(Mg0.5Sn0.5)O3 ceramics prepared by the conventional solid-state method have been investigated for application in mobile communication. B2O3 was selected as a liquid sintering aid to lower the sintering temperature of La2.98/3Ba0.01(Mg0.5Sn0.5)O3 ceramics. It was found that the X-ray diffraction patterns of the La2.98/3Ba0.01(Mg0.5Sn0.5)O3 ceramics exhibited no significant phase difference with 0.25 wt% B2O3 additive at different sintering temperatures from 1350 to 1550 ??C. The maximum values of the dielectric constant and the quality factor multiples resonant frequency (Q??f) can be obtained when the La2.98/3Ba0.01(Mg0.5Sn0.5)O3 with 0.25 wt% B2O3 additive were sintered at 1400 ??C for 4h. The temperature coefficient of resonant frequency ??f (-72 ppm/ ??C) was measured for La2.98/3Ba0.01(Mg0.5Sn0.5)O3 ceramics with 0.25 wt% B2O3 sintered at 1400 ??C for 4 h.