The propagation expression of a broadband laser passing through a dispersive wedge is derived on the basis of the Huygens–Fresneldiffraction integral. Smoothing effects caused by the phase perturbation of the dispersive wedge on the intensity profiles are investigatedin detail. The phase perturbation of the dispersive wedge induces a relative transverse position shift between the diffraction patterns ofdifferent frequency components. The relative transverse position shift is of great benefit to the fill of the intensity peaks of some patternsin the valleys of others when these patterns are overlapped and thus the smoothing effect is achieved.