Abstract: Nanometer powder of Mn-Co-Ni oxides was prepared by using co-precipitation method with oxalic acid as precipitator, and it was tested and analyzed using TG、DTA、XRD、SEM technology. The result shows that the powder of Mn-Co-Ni oxide can be obtained with following properties: grain size about 9nm, near-spherical shape particle with diameter about 50~100nm , narrow range of the particle distribution. And these properties meet the requirement for making Co-Mn-Ni-O NTC thermistors.