In this study, low-temperature fired CaMg_1−xLi_2xSi₂O₆microwave dielectric ceramics were prepared via the traditional solid-state reaction method. In this process, 0.4 wt% Li₂CO₃-B₂O₃-SiO₂-CaCO₃-Al₂O₃(LBSCA) glass was added as a sintering aid. The results showed that ceramics consisted of CaMgSi₂O₆as the main phase. The second phases were CaSiO₃always existing and Li₂SiO₃occurring at substitution contentx> 0.05. Li⁺substitution effectively lowered sintering temperature due to 0.4 wt% LBSCA and contributed to grain densification, and the most homogeneous morphology could be observed atx= 0.05. The effects of relative density, the second phase, and ionic polarizability on dielectric constant (ε_r) were investigated. The quality factor (Q×f) varied with packing fraction that concerned the second phase. Moreover, the temperature coefficient of the resonant frequency (τ_f) was influenced by MgO₆octahedral distortion and bond valence. Excellent dielectric properties of the CaMg_1−xLi_2xSi₂O₆ceramic was exhibited atx= 0.05 with ε_r= 7.44,Q×f= 41,017 GHz (f= 15.1638 GHz), and τ_f= −59.3 ppm/°C when sintered at 900 °C. It had a good application prospect in the field of low-temperature co-fired ceramic (LTCC) substrate and devices.