Precise physical experiments place strict requirements on target illumination uniformity in inertial confinement fusion. Currently, the main stream of beam smoothing technology adopted in solid-state laser driver is smoothing by spectral dispersion (SSD). The SSD based on wave-guide phase modulator is experimentally studied here. The experimental results indicate that this phase modulator can easily broaden the narrow-band light generated from a DFB laser to 0.1 nm to 1.5 nm bandwidth. The far-field analysis indicates the experimental results are in good accordance with the simulation results. In the meantime, nearfield modulation around 100 μm after the dispersion grating could be smoothed significantly. The research lays experimental basis for the optimization of beam smoothing in high-power laser facility.