Composite materials have good mechanical properties. In order to solve the difficult process of composite materials, this paper proposes to use a method of ultrasonic milling on the composite materials processing, we mainly studies the effect of the length of the arbor, arbor diameter and arbor end milling platform on the acoustic resonant frequency, amplitude, and anti-resonance frequency. With the decreased in the length of the tool bar, tool bar's resonant frequency increased，and the oscillation amplitude also obviously increased. In the vicinity of 35 KHz amplitude of vibration are largest. Along with tool bar diameter's increasing, the resonant frequency is increases gradually. Milling platform has little effect on the resonant frequency and amplitude.