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A novel four-ring photonic crystal fiber (PCF) structure with two different air-hole sizes is proposed with nearly zero ultraflattened dispersion characteristics. Through optimizing only three geometrical parameters, two air-hole diameters, and one hole pitch, the ultraflattened zero dispersion PCF can be efficiently designed. As an example, a four-ring PCF with flattened dispersion of ±0.25 ps/km/nm from 1.295- to 1.725-μm wavelength is numerically demonstrated. The corresponding design procedures for the novel PCF are also presented in this letter.