Abstract: Titanium alloy slender shaft parts belong to the typical difficult-to-machine material parts. Turning process would not only exist cutting force, cutting temperature, tool wear serious problems, there would be relatively low stiffness, and cutting force under the action of bending deformation was prone to such problems. Based on the finite element simulation model, the ultrasonic parameters were analyzed to carry out ultrasonic vibration turning experiments on the basis of the analysis of the force and deformation of the slender shaft turning. The results showed that with the increasing depth of cut, the cutting force increases. At a certain position, the friction between the front tool face and the chip reversed, which makes the cutting force change in the opposite direction. Two-dimensional ultrasonic vibration turning, the amplitude of the change of the main cutting force when the ultrasonic frequency was 30 kHz obviously greater than 20 kHz, but in the same case the radial cutting force in the ultrasonic frequency of 20 kHz was obviously greater than the amplitude of the change of the 30 kHz, and the maximum difference in the radial cutting force was 14.81 N. Three-dimensional vibratory turning was stronger than two-dimensional ultrasonic vibratory turning in improving the stability of cutting force. Within the scope of cutting speed of 15−25 m/min, the main cutting force of TC4 titanium alloy slender shaft increased with the increase of cutting speed, and the main cutting force increased with the increase of feed. By comparing the two processing methods, it can be found that the two ultrasonic vibration turning main cutting force with the cutting parameters of the change trend were basically the same. The results will provide theoretical support for ultrasonic vibration assisted machining.