A sectional magneto-optic fiber Bragg grating (MFBG) is the grating structure fabricated by writing multi-subsectional gratings onto a magneto-optic fiber. According to the coupled-mode theory for uniform MFBGs and the boundary continuity conditions of the electromagnetic field,the spectral characteristics of the circularly polarized light in the multi- sectional MFBG were theoretically studied. The research indicates that,the optical spectrum of the one-sectional MFBG is identical with that of the uniform MFBG,and the theoretical results of polarization dependent loss are consistent with the experimental data. The analysis also shows that sectional MFBGs are useful for photonic information processing such as adjustable comb filtering,optical clock extraction and tunable dispersion compensation.