Sintering of a ZrO2-DaO nanocrystalline system under the action of a constant magnetic field within the temperature interval 1200-1400A degrees C gives rise to predetermined changes in microstructure and morphology of the particles. A method is proposed for hardening ZrO2(CaO) ceramics and a quantitative estimation of its contribution into the changes of its mechanical properties and fine crystalline structure parameters. A possibility is demonstrated for using constant magnetic field for deliberate changes of microstructure and mechanical properties of porous ceramics.