The characteristics desired for magnetic materials from the application point of view are: high saturation magnetization, high magnetic permeability, high Curie temperature, high electric resistivity and low cost. Li-Zn ferrite is one of the most important magnetic materials due to its high magnetization and square hysteresis loop. It was found that the composition Li0.3Zn0.4Fe2.3O4 has the maximum saturation magnetization in the Li-Zn ferrite series. I aimed to improve the electric and magnetic properties of such a reference sample using different valent elements (Ca, Bi, Zr and Nb). They were already used as additives and produced different phases. In my work, I prepared Li-Zn ferrite substituted by these four elements with different concentrations by standard ceramic method. Magnetic properties were studied through measuring the magnetization, the initial permeability, Curie temperature and hysteresis loop parameters. Electric properties were studied through temperature dependence of the dc resistivity. Thermoelectric power and the conduction mechanism were discussed. Frequency dependence of the dielectric constant, dielectric loss and ac resistivity were measured and discussed.