The modal cut-off properties and resonant properties of Ge-doped photonic crystal fiber Bragg grating (PCFBG) with regular octagonal cladding air holes are investigated by using the mode coupling theory and the transmission matrix method, and the modal cut-off condition and the mode of transmission are given. To meet the need of the resonant wavelength, a method is designed by changing the period of the grating based on the phase matching conditions. The reflection spectrum of the grating simulation result is obtained. It is found that with properly chosen structural parameters, needed single-mode transmission and resonance with tailored main resonant peak can be realized using the PCFBG. This kind of PCFBG can thus be better applied to fiber sensing areas.