These powder properties were investigated and prepared of ultrafine Mn-Zn ferrite powder by Direct-wet process from variation of oxidation condition. H2O2 oxidation the products were ultrafine spherical particles of about 400${AA}$ in diameter and superparamagnetics. H2O2 and Air oxidation, Coexistance ultrafine spherical particles of about 400${AA}$ and cubic particles of about 1000${AA}$. The products were constructed of superparamagnetic and ferromagnetic particles, and Magnetization were about 30 emu/g. Air Oxidation, Above 6 hr Air 120 ι/hr and 4 hr of Air 180 ι/hr were uniform cubic particles of above 1000${AA}$. The products were ferromagnetic particles and Magnetization of above 45 emu/g.