Abstract: Dual-mode ferrite devices include such as dule-mode phase shifter,circular polarization phase shifter,rotary-field phase shifter,dual-mode polarizer variable and so on.It is comprised of a number of dual-mode ferrite waveguides cascaded,which is formed by all types of combination.According to different methods of magnetization,there are quadrapole magnet field,dipole field,longitudinal magnet field,and their compound field in each basic ferrite section.A generalized and unitized theory for dual-mode ferrite devices is developed in this paper that has been dealed with perturbation field theory.Furthermore,the polarization matrix and perturbation field theory has been combined each other and through some of examples,the result calculated for the various of dule-mode ferrite devices has confirmed the exactitude of theory.