The dispersion properties of optical wave in photonic band gap guiding photonic crystal fibers (PBG-PCF) were analyzed by the finite differential time domain method. The result demonstrates that: the point defects and the dislocation of air holes make the zero-dispersion-point move to the long-wavelength side, but the change of the shape of the air columm makes it move in the opposite direction. All kinds of defects make the dispersion curves flatten.