The dispersion and mode characteristics in a dual-concentric-core photonic crystal fiber, based on pure silica, are simulated by the multipole method. The fiber exhibits very large negative dispersion due to anticrossing of two individual inner core and outer core modes. Near the wavelength of $1.55\mathrm{\mu m}$ , we could obtain narrowband dispersion-compensating fiber with dispersion values of $-\mathrm{23,000}\mathrm{ps}/\mathrm{km}/\mathrm{nm}$ , broadband dispersion-compensating fiber with dispersion values from $-1000\mathrm{ps}/\mathrm{km}/\mathrm{nm}$ to $-2500\mathrm{ps}/\mathrm{km}/\mathrm{nm}$ over a $200\mathrm{nm}$ range, and kappa values near $300\mathrm{nm}$ , which matched well with standard single mode fiber. It shows that even if there are some changes in the structure parameters during fabrication, these fibers can still maintain a fine dispersion-compensating property.