Up to now the amplitude amplification of ultrasonic vibration cutting system is achieved by the longitudinal vibration horn (one-stage amplitude amplification bar). The two-stage amplitude amplification function and mechanism of step-type cutter bar in vibration system are studied through theoretical analysis and experiment. The new system is not limited to the use of the longitudinal vibration horn to amplify the amplitude at the tool tip, thus offering the theoretical basis for developing new vibration cutting systems. Up to now the amplitude amplification of ultrasonic vibration cutting system is achieved by the longitudinal vibration horn (one-stage amplitude amplification bar). The two-stage amplitude amplification function and mechanism of step-type cutter bar in vibration system are studied through theoretical analysis and experiment. The new system is not limited to the use of the longitudinal vibration horn to amplify the amplitude at the tool tip, thus offering the theoretical basis for developing new vibration cutting systems.