The dynamic characteristics of the GMR filter composed of dual-period gratings are explored. Gratings consisting of several gloves and slits that generate reflection and transmission properties within each period are considered. It is found that the proposed composite grating can be designed to enhance as well as offset the diffraction orders of TE and TM modes depending on the number of dual-period grating. In order to derive the general characteristics of diffraction power, numerical analysis is performed by applying the modal transmission-line theory based on eigenvalue problem. As a result of the numerical analysis, it is confirmed that a simple and effective GMR filter can be implemented by selectively manipulating the resonance mode of the composite structure, which is useful for designing NIR broad-band filter, emitter and absorber.