A temperature-stable modified NiO—Ta2O5-based microwave dielectric ceramic material and a preparation method thereof are provided. Using ion doping modification to form solid solution structure is an important measure to adjust microwave dielectric properties, especially the temperature stability. Based on formation rules of the solid solution, ion replacement methods are designed including Ni2+ ions are replaced by Cu2+ ions, and (Ni1/3Ta2/3)4+ composite ions are replaced by [(Al1/2Nb1/2)ySn1-y]4+ composite ions, which considers that cations with similar ionic radii to Ni2+ and Ta5+ ions can be introduced into the NiTa2O6 ceramic for doping under the same coordination environment (coordination number=6), and therefore a ceramic material with the NiTa2O6 solid solution structure can be obtained. The microwave dielectric ceramic material with excellent temperature stability and low loss is finally prepared by adjusting molar contents of each of doped ions, and its microwave dielectric properties are excellent.