Abstract: Large-diameter titanium alloy seamless tube is a large-scale thin-walled part, which is mainly used for external processing by turning, and the large radial cutting force is easy to cause the deformation of the workpiece. Orthogonal turn-milling has a relatively small radial cutting force on machining the outer surface, which is a new method that can better machine this type of part. Through the three-factor and three-level orthogonal simulation experiments, the influence of cutting parameters on the radial cutting force of machining large-diameter titanium alloy seamless tube is studied by eccentric orthogonal turn-milling, established an empirical formula for radial cutting force. The results show that the influence of cutting parameters on the radial cutting force is in the order of a_p>f_z>v_c, and the efficiency of cutting can be improved by appropriately increasing the feed per tooth.