In this paper, the Li3(Mg1−xNix)2NbO6 (0.02 ≦ x ≦ 0.08) ceramics are prepared by a solid state reaction method. The effects of Ni2+ substitution on the microwave dielectric properties, microstructure and sintering properties are investigated systematically. The XRD patterns reveal that all the samples could form solid solution with a single Li3Mg2NbO6 phase in the sintering process. The variation in Q × f values is similar to that in bulk density, and tremendous improvement of Q × f values could be attributed to bigger grains and high densification. Since the more polarizable Mg2+ ion is replaced by the less polarizable Ni2+ ion, the permittivities decrease almost linearly with increasing Ni2+ content. Otherwise, with the x value increase from 0.02 to 0.08, the τf values could be effectively adjusted to near zero, but the decreasing porosity-corrected permittivities would damage the stability of crystal structure, which make the τf values shift toward the negative direction. In general, the Li3(Mg0.96Ni0.04)2NbO6 ceramics sintered at 1175 °C for 6 h exhibit superior microwave dielectric properties of εr ~ 15.22, Q × f ~ 126,784 GHz, τf ~ − 2.63 ppm/°C, which demonstrate that the ceramics could be selected as a promising low loss and temperature stable material for future application.