This study focused on the side milling surface roughness of titanium alloy under various cooling strategies and cutting parameters. The experimental results show that the cooling strategies significantly affect the surface roughness in milling Ti-6Al-4V. Surface roughness (Ra) alterations are investigated. Cutting fluid strategy made nearly all the smallest and most stable roughness values. The surface roughness values produced by all cooling strategies are obviously affected by feed, radial depth-of-cut and cutting speed. However, axial depth-of-cut has little influence.