In this study, the spinel solid solution ceramics (1-x)LiFe5O8-xLi(2)ZnTi(3)O(8) (0x1) were prepared via the solid-state reaction method. The phase evolution, sintering behaviors, microstructures, magneto-dielectric properties, and microwave dielectric properties were systematically investigated. The XRD and SEM analysis indicated that the LiFe5O8 phase and the Li2ZnTi3O8 phase were almost fully soluble in each other at any proportion. Meanwhile, the evidence of ionic substitution has been directly observed at the atomic scale by means of scanning transmission electron microscopy, which is further confirmed by the Raman spectroscopy. Evidence shows that the magnetic and dielectric properties are quite sensitive to the compositions. The optimal results with remarkable magneto-dielectric properties of =38.2, tan=0.25, epsilon=19.6, tan(epsilon)=8x10(-3) at 1MHz, and epsilon=19.1, Qxf=10400GHz at about 7GHz have been obtained in 0.25LiFe(5)O(8)-0.75Li(2)ZnTi(3)O(8) sample. The design of complex spinel solid solution can generate novel magneto-dielectric single-phase ceramics combining both high permeability and good dielectric properties, which provides a way in developing multifunctional materials for applications in electronic devices.