Abstract: Surface roughness measurement based on digital holography was carried out. The tested surface roughness parameters were calculated from the surface profile which was mapped from the reconstructed phase distribution of digital hologram. Firstly, the standard calibration plate and high-resolution panel were taken as the tested samples to reconstruct errors and test the repeatability of the digital holography measurement system,involving the lateral size error and the height error. The reconstruction error and repeatability error for lateral size were 1.11%, 0.61%, respectively. And the errors for height were 11%, 1.8%, respectively. Then an ordinary coated reflector was taken as a sample, and its surface roughness values along 3 segments of evaluation length were 0.010 37 m, 0.010 33 m, and 0.009 67 m, respectively(15 sampling lengths).