Abstract: TC25 titanium alloy is an ideal material for aeroengine because of its outstanding mechanical properties that can be provided at high temperature. Surface roughness is used as an important evaluation criterion of the surface processing quality. Based on the results of orthogonal experiment, the influence of milling parameters on surface roughness is analyzed by the method of extreme difference analysis. The results show that the cutting feed f_z has the most significant effect on the surface roughness. The extreme difference of empty column R=0.026, which indicates that factors and levels are reasonable. A₃B₁C₁D₁ is a set of optimized parameters. The predictive model for surface roughness of milling titanium alloy TC25 is established by multiple linear regression analysis. Variance analysis is used to verify saliency of the predictive model. Finally, the obtained optimal parameters and the accuracy of predictive model are validated by confirmation test.