Abstract: Magneto-optic fiber gratings are a class of special fiber gratings with magneto-optical effects, which are useful for intrinsic magnetic field sensing and realizing magnetic controlled photonic information processing. The magnetic field sensitivity of polarization-dependent loss for left-/right-handed circularly polarized light in sectional magneto-optic fiber Bragg gratings (MFBGs) is analyzed by using the piecewise-uniform grating model and it is shown that the central section of uniform MFBGs is most sensitive to magnetic field. The F-P structure of sectional MFBGs is presented, which is superior to the corresponding uniform MFBGs for measuring the polarization-dependent loss in the range of small magnetic field.