This paper proposes an accurate method to calculate the permittivity and permeability of ferrites simultaneously at the demagnetized state. The eigenvalue equations for the resonator model can be obtained by applying the boundary condition of the structure of the resonator at both demagnetized and magnetized states. The complex permeability and permittivity are computed from the measured resonant frequencies and unloaded quality factors of the resonator using the mode splitting phenomenon. To verify the calculated magnetization values, the magneto-static simulation is performed by using CST EM studio based on the measured data of B-H curve. The measured complex permeability and permittivity of the demagnetized ferrite are verified by comparing with cavity perturbation method and statistic equation.