To investigate the polishing effect of fiber optic continuous laser on milling titanium alloy surfaces, this paper conducted 16 sets of orthogonal experiments L16 (43) to study the effects of laser power, scanning speed, and scanning spacing on the surface roughness of Ti6Al4V samples after milling in the fiber optic continuous laser polishing process. The optimal parameter combination for fiber optic continuous laser polishing process was determined through parameter optimization. This article focuses on how to reduce the surface roughness of titanium alloy after milling. Based on the priority of the influence of various process parameters on surface roughness in laser polishing technology, a numerical simulation and prediction model of laser polishing on titanium alloy surface roughness is established. The optimal process parameters predicted by the simulation model are used to conduct processing experiments on the sample surface. The experiment results of the final polishing process show that among the explored laser polishing process parameters, the priority of the influence of various factors on the sample’s surface roughness is in the sequence of laser power scanning speed scanning spacing. The established numerical model for titanium alloy surface polishing predicts the prefer optimal process parameters as below: laser power P = 290 W, scanning speed v = 70 mm/s, and scanning spacing d = 0.01 mm. Under the prefer optimal process parameter combination, compared with the original titanium alloy surface roughness of 2.831 μm, the surface roughness of the material after laser polishing decreased by 85.44%, and the surface roughness after laser polishing was 0.412 μm.