The laser irradiation non-uniformity of target is required below 5% in inertial confinement fusion (ICF). The scheme of combining smoothing by spectral dispersion (SSD) and lens array (LA) is introduced to meet the above demand, based on the present application LA. The feasibility of the scheme is analyzed by numerical simulation. It shows that the irradiation non-uniformity of focal spot falls down from 14% with LA to 3% with SSD and LA. The result power spectrum analyses of focal spot show that the smoothing effect is caused by middle and high frequency intensity suppression. The scheme can improve the ability of beam smoothing. The results are useful for practical application.