In order to improve its vibration transmission and amplitude output characteristics, a horn for rotary ultrasonic machining with a tapered locating nodal surface was designed based on the analytical method, and optimized by the prestress modal analysis and harmonic response analysis.27 optimization design points were established making use of the response surface optimization method.The first, second and third optimization objectives are maximizing the amplification factor, minimizing the maximum equivalent stress and closing the resonant frequency to the theoretical design frequency, respectively.A 5-order modal frequency response surface validation method was proposed, and the optimal solution of the optimal design points was verified by the results of (2—6) order 5-mode frequency response surface analysis.The results show that, based on the proposed method, the optimized horn can improve the amplification coefficient, reduce the maximum equivalent stress, make the resonant frequency close to the theoretical design frequency, and improve the energy efficiency of ultrasonic machining.It has a certain guiding significance for the research and development of the performance of rotary ultrasonic machining equipments.