Nanosized powders of Ni0.5Zn0.5 Fe2O4 with well-developed spinel phases were prepared by the hydrothermal method. An average particle size about 10 ~ 20 nm of Ni-Zn ferrite powder is obtained. Heat treatment and the concentration of reagent are two factors to get large particles.The magnetic hysteresis behavior of the absorber are affect by the cationic dopants and the core-shell structure which Ag is used as the core. The electromagnetic properties of permittivity and permeability are measured in 2-15GHz frequency range.There are different observations of hysteresis effect by varing particle sizes and doping different cationic dopants and doping different ratio of Ag . The sharp decrease of real part of permeability (μ?) shifts to higher frequencies while the sharp peak of imaginary part of the permeability (μ?) also shifts to correspond high frequencies by heat treatment .There is an evidence that the sharp peak of real part (μ?) and imaginary part (μ?) of the permeability are shifted to lower frequencies by different cationic dopants . The sharp peak of real part (μ?) and imaginary part (μ?) of the permeability are shifted to higher frequencies with the increase of Ag. According to Debye-Hertz potential equation, microwave absorption data(reflection loss) are calculated with the four parameters(ε?、ε?、μ?、μ?) ,frequency and thickness of layer.