Abstract: The influence of grating length, air filling factor and grating period of photonic crystal fiber Bragg grating (PCFBG) on slow light was investigated by improved full vector Effective Index Method (IEIM) and the Coupled-mode theory. The results indicate that the slow light peak wavelength of PCFBG shows a blue shift as the filling factor increases, and the slow light of PCFBG decreases gradually while keeping the grating length and grating period as constants; 1.06 centimeter-long PCFBG can produce linear delay of about 52 ps; slow light of PCFBG increases with the grating length increase; the maximum group velocity of c/371 exists in the vicinity of the side-lobes under optimizing the structure parameters.