A new low-fired dielectric material derived from CaMg0.9Zn0.1Si2O6 (CMZS) ceramics with high quality factor was synthesized by solid-state reaction method. The effects of MgF2 addition on the sinterability, phase composition, crystal defects, and microwave dielectric properties of CMZS were investigated. MgF2 was proved not only to lower the sintering temperature to similar to 1000 degrees C but also to remarkably modify the microwave dielectric properties of CMZS. In addition to the main diopside phase, forsterite was identified as the secondary phase in all MgF2-doped samples. Dielectric temperature spectra showed that MgF2 induced significant dielectric relaxations associated with oxygen vacancy defects to CMZS. Thermally stimulated depolarization current was, therefore, considered to obtain the defects associated with extrinsic microwave dielectric loss mechanisms. Compared with undoped CMZS, although the concentration of oxygen vacancies showed a notable increase in the 5 wt% MgF2-doped CMZS, the Qxf values were still improved. Here, with proper MgF2-doping, it demonstrated that the microwave dielectric loss was basically influenced by phase composition. The excellent characteristics of epsilon(r) = 7.78, Qxf=151800GHz, and (f) = -26.40ppm/degrees C were achieved from the 5 wt% MgF2-doped specimens sintered at 1000 degrees C.