In this paper, an ultrasonic anti-friction vibrator is proposed to reduce the friction of ball screw pair. The vibration exciter and the nut of ball screw pair are connected at the flange by bolts, and the friction reduction of the ball screw pair is realized by exciting the first torsional vibration mode of the anti-friction vibrator. The modal analysis of the anti-friction vibrator is carried out using the finite element method. The orthogonal experiment on the sleeve length of the exciter, the thickness of the exciter flange and inner diameter is carried out. The best combination is obtained, and the size of the main structure is determined. A prototype is fabricated. Finally, the feasibility of the antifriction method is verified by the experiment on the prototype of the anti-friction vibrator.