For a more accurate numerical simulation, the generalized nonlinear Schrdinger equation is adopted to describe the evolution of ultra-short laser pulse propagating in photonic crystal fibers, and solved by using the second-order split-step Fourier method. The nonlinear propagation of ultra-short pulse with the same pulse width and energy, and generation of super-continuum spectrum are numerically simulated in different dispersion regions of photonic crystal fibers. In the different dispersion regions, the influence of high-order dispersion and nonlinear effects on the generation of super-continuum spectrum and pulse profile evolution are analyzed. The results show that, when the central wavelength of the input pulse is in the normal or abnormal dispersion regions, the super-continuum spectrum of short-wave band or long-wave band is obtained respectively (respect to the central wavelength). When the central wavelength is at the zero dispersion wavelength point of photonic crystal fibers, a flat super-continuum spectrum of the whole wave-band can be generated by combining the influence of high-order dispersion and nonlinear effect.