The Mn-Zn ferrite of thermomagnetic effect was prepared by coprecipitation. The samples were tested by LS Particle Size Analyzer for precursor and the hysteresis loop, XRD and thermomagnetic tests were also carried out. The results show that the best pH value is 4, the best preserved temperature is 70℃ and the best preserved time is 1.5 h. We use reversal drop-method to add reagent. Being placed under alternative magnetic field, the samples have the obvious thermomagnetic effect. Comared to dry preparation, the Mn-Zn ferrite prepared by wet preparation has better quality. （From : No.1, 2006 Glass & Enamel）