Abstract: The dispersion properties of photonic crystal fibers were studied with finite element method (FEM)by changing the diameter of the air-holes belonging to the first three rings.It was found that zero dispersion wavelength could be shifted in the range of 1100nm～1800nm by adjusting the air-hole diameter of the first, the second or the third ring.Photonic crystal fibers with nearly zero flattened dispersion over a very broad spectral range can be designed through choosing the suitable air-hole diameter of the first,the second or the third ring.The results is useful for photonic crystal fibers design.