A theoretical investigation with the method of split-step Fourier is presented on the nonlinear propagation and supercontinuum generation of a femtosecond laser pulse in a photonic crystal fiber. The impact of high-order dispersion and nonlinear effects on spectral shape and band width is simulated and analyzed. It is found that soliton self-frequency shift is generated in a photonic crystal fiber. It is also found that intrapulse stimulated Raman scattering and self-phase modulation result in the fine spectral substructure of the supercontinnum. The band width and smoothing of the supercontinuum are found to be related to the higher-order dispersion and the power of the initial laser pulse.