Abstract: In order to remove the surface defects of titanium alloy bar and to reduce the surface roughness, titanium alloy bar was cut by centerless lathe. In this paper, the response surface method is used to design the experiment. Through the regression analysis of the experimental data, the surface roughness prediction model is established based on the processing parameters(spindle speed, cutting depth, feeding speed). The influence law of turning process parameters and their interaction on the surface roughness is analyzed and the optimal turning process parameter interval is obtained. The results show that the order of the influence of turning process parameters on the surface roughness of the process index is a_p > f > V. In the interaction of process parameters, the interaction of f-a_p has the greatest influence on the surface roughness. The combination of process parameters determined in the optimal turning process parameter interval can meet the production requirements of surface roughness less than 0.8 μm.