We measure the surface roughness of the mechanical parts based on digital holography. A digital off-axis hologram recording setup for reflective samples is built. Firstly, the height reconstruction error 2.3% of the setup is calibrated by using the quartz step height standard (VLSI-SHS-880QC). Then, the standard scribed-line model and the grinding roughness specimen are selected as the test samples and their surface roughness are 0.095 6 μm and 0.025 3 μm, with errors 6.3%, 0.9%, respectively. The results are in good agreement with the given roughness parameters. At last, we also analyze the window effect of the filter on the roughness measurement value based on digital holography. In conclusion, the paper demonstrated effectively that the digital holography could provide the surface feature for the roughness measurement with high accuracy.