Abstract: To investigate the influence of the milling parameters on surface roughness during machining TC4 titanium alloy by the high-feed milling using a bull-nose end mill. Through orthogonal experiments and single-factor tests, an empirical formula for surface roughness was established. Additionally, MOPSO was employed for multi-objective optimization, targeting minimum surface roughness and maximum material removal rate (MRR). The results reveal that the order of significance for the milling parameters on surface roughness is a_p>v_c>f_z, and surface roughness was found to be positively correlated with cutting speed, feed per tooth, and depth of cut. Finally, this resulted in 20 sets of balanced milling parameters. This multi-objective optimization method can predict the milling parameter combinations that balance the requirements of low surface roughness and high material removal rate during high-feed milling of TC4 titanium alloy using a bull-nose end mill.