Manganese- Zinc ferrite is one of the most important spinel ferrites which is used in the electronics applications. These ferrites have an open lattice and can tolerate large amounts of the other metallic ions in their lattice. One of these divalent ions that can sit in the unit cell of Mn-Zn ferrites is Magnesium. Mn-Mg-Zn ferrites are new materials which is thought to be a good candidate for dielectric applications. In this work, a suitable relative values of raw materials for preparing pure Mn-Mg-Zn ferrite powder have been determined. It is carried out by using XRD experiments. The optimum temperature and time of calcination were also investigated by DTA/TGA, XRD and SEM techniques.