The effects of the gamma ray irradiation on the, microstructural and magnetic properties of the composite (1-x) (Ni0.8Zn0.2Fe2O4) + x (BaTiO3) where x = 0%, 20%, 40%, 60%, 80% and 100 %BT content have been investigated. All samples were exposed to gamma radiation dose in range 310 kGy with dose rate 1.4 kGy/h at room temperature using 60Co radioactive source at irradiation cell (medical sterilizer type CM-20). From the X-ray diffraction analysis, it was found obviously that the lattice parameters and average grain size have been affected, for all irradiated samples. The initial permeability at Curie temperature for all samples were sharply decreases after irradiation. The calculated values of diffusion coefficient of Oxygen vacancies, the concentration of Oxygen vacancies and the activation energy of diffusion process were calculated before and after irradiation. From the results we conclude that the material after irradiation can be used for the Gamma ray detection.