Abstract: In the milling process, the reasonable selection of the process parameter range plays an important role in controlling the surface roughness, which is closely related to the performance of parts. In order to study the influence of milling process parameters on surface roughness and obtain the stability region of process parameters, a second-order regression model of surface roughness Ra was established based on the response surface methodology. The multi-parameter global relative sensitivity analysis was used to determine the sensitivity of Ra to milling process parameters, and the sensitivity of Ra to single parameter intervals was studied through single parameter local sensitivity analysis. The stable range and unstable range were divided according to the sensitivity curve. After analysis, the stable range of process parameters was clarified. The results show that the stable range of milling process parameters is: spindle speed7 000 r/min, 8 000 r/min, feed speed100 mm/min, 200 mm/min, axial cutting depth0.03 mm, 0.05 mmand radial cutting depth0.1 mm, 0.2 mm, and the reliability of the stability domain are verified.