Two-dimensional performance of uniform irradiation with the smoothing by spectral dispersion (SSD) and distributed phase plates (DPP) is researched on the SG II laser facility. The results of experiments in free space show that 1D-SSD makes the root mean square (RMS) focus drop to 0.3685 from 0.7634 (without SSD), and 2D-SSD supplied RMS is 0.2638. Other appraising methods of focus verify the conclusion. This experiment is especially meaningful for on-line 2D-SSD experiment.