In　this　paper,　a　strategy　for　preparing　MgAl2-x(Mg0.5Ge0.5)(x)O-4　(0　＜=　x　＜=　0.12)　solid　solution　ceramics　through　the　substitution　of　(Mg0.5Ge0.5)(3+)　for　Al3+　in　the　octahedral　lattice　of　spinel　crystal　structure　A(tetra)B-2(octa)O-4　via　traditional　high-temperature　solid-state　reaction　method　is　presented.　The　intrinsic　and　extrinsic　factors　influencing　their　microwave　dielectric　properties,　including　the　inversion　degree　of　A/B　lattice　sites　(lattice　occupancy),　bond　length　and　bond　valence,　as　well　as　grain　sizes,　were　investigated　using　Rietveld　refinement　of　X-ray　powder　diffraction　data　and　scanning　electron　microscopy.　To　verify　the　applicability　for　the　next-generation　5　G-n257/n258　millimeter　wave　frequency　band,　the　Qxf　values　were　tested　within　the　frequency　range　of　12-25　GHz.　Notably,　MgAl1.91(Mg0.5Ge0.5)(0.09)O-4　ceramics　exhibited　a　high　Qxf　value　of　105,　384　GHz　@11.83　GHz,　low　epsilon(r)　of　8.7,　and　tau(f)　of　-66.4　ppm/degree　celsius.　SrTiO3　was　added　to　tune　the　tau(f)　to　a　near-zero　value　of　+2.6　ppm/degree　celsius　with　high　Qxf　value　of　51,　152　GHz　@11.53　GHz　and　epsilon(r)　of　9.91.　Finally,　a　microstrip　filter　with　a　center　frequency　of　3.6　GHz　was　designed　using　this　composite　ceramic,　successfully　demonstrating　its　practical　application　in　the　low-frequency　band　of　5　G　networks.