When the core index is increased by using doped GeO2 technology in photonic crystal fiber (PCF), light is more easily confined by not only the air holes, but also the raised-index core. By numerical solving Helmholtz equation with finite differential (FD) method, some performances were studied about PCF that transverse cross sections consist of a central high-index defect in a regular triangular array of air holes. The dispersion difference is visible under all kind of doped proportion in core when the core and air hole sizes are fixed. Higher doped proportion in core will bring higher effective index of PCF and make the dispersion parameter decreasing. Furthermore, increasing the air hole sizes with fixed core size and index will make the dispersion become higher, effective index decreasing and effective area of modal field decreasing. Especially, the changing trend is little different under all kinds of doped proportion in core.