Abstract: The Mg₄Nb₂O₉-CaTiO₃ composite ceramics were synthesised by the conventional solid-state reaction. The effects of Li₂CO₃-V₂O₅ (LV) addition on the sintering behavior, microstructure and microwave dielectric properties of Mg₄Nb₂O₉/CaTiO₃ ceramics were investigated. It is found that an amount LV co-doped can effectively low the desification sintering temperature to 1200℃ of Mg₄Nb₂O₉/CaTiO₃ ceramics. Two-phase system was confirmed by the XRD and EDX spectrum analysis. A near zero temperature coefficient of resonant frequency was obtained. Inparticular, a new Mg₄Nb₂O₉-CaTiO₃ ceramics with 1.5% mass fraction of LV doped sintered at 1200℃ for 5h exhibited excellent microwave dieletric properties of ε=23.29, Qf=23460GHz and τ_f=1.0×10^-6℃^-1. It is proposed as a candidate subatrate material for GPS microstrip antenna.