To improve laser irradiation uniformity, experimental research on smoothing by spectral dispersion (SSD) and continuous phase plate (CPP) is carried out on the technical integration line (TIL). A bulk phase modulator with 9.2 GHz modulation frequency is adopted. The output spectrum of the phase modulator is stable and the residual amplitude modulation is quite small. The experimental results indicate that when the number of color cycles (Nc) is adopted to be 1, imposing of SSD in this divergence does not lead to pinhole closure in the spatial filters of the preamplifier and main amplifier. The contrast of the focal spot with 95% energy included with SSD and CPP drops to 0.47 compared with 1.71 without SSD and CPP. When the pulse width of the third harmonic wave is 1 ns and its energy is 1115 J, no damage is found in CPP and other final optics. The experiment solves some key techniques by using SSD and CPP on high-power laser facilities, and provides sound basis for the upcoming physics experiment.