The evolutional waveforms and spectrograms of sech, gaussian pulse (m=1) and supergaussian pulse (m=5) generated in normal dispersion region of high nonlinear fiber were numerically studied. The results indicate that the tail at both front and back edge of the pulse not only affects spectrum broadening, but also the flatness of supercontinuum. The chirp of pump pulse has little impacts on the generated supercontinuum. The pulse with high power, steep edge and small tail is preferable to generate wideband and flat supercontinuum.