Ultrasonic processing technology has been involved in many fields, ultrasonic amplitude change rod is one of the important components of ultrasonic vibration system in ultrasonic processing equipment. In order to compare and analyze the multifrequency ultrasonic horn, the conical horn is taken as an example. The 25 kHz, 30 kHz, 35 kHz vibrational frequency horn was selected, and the steady state and harmonic response of multifrequency horn were studied with analysis by using ABAQUS largescale nonlinear finite element (FE) simulation software. Firstly, the steady state of the multifrequency horn was compared and analyzed, then the force load was added to the tapered horn, and the displacement and stress curves of the horn with different frequencies were compared and analyzed. Finally, the changing rule of multifrequency variation of amplitude rod is obtained in steady state analysis and harmonic response process.