The work aims to reveal the brittle-ductile transition characteristics of rotating ultrasonic vibration on hard-brittle materials and the influence of processing parameter on the critical cutting depth of zirconia ceramics. Based on the fracture experiment, the critical condition of brittle-ductile transition of hard-brittle materials processing by rotary ultrasonic vibration was analyzed theoretically, and the comparison testing between rotary ultrasonic vibration scratch and normal scratch was carried out. Under the same test conditions, compared with the critical cutting depth of brittle-ductile transition on normal scratch, ultrasonic vibration scratch has a higher value. The critical cutting depth of brittle-ductile transition can be effectively increased by increasing the ultrasonic energy, and the critical cutting depth of brittle-ductile transition in longitudinal-torsional resonance is higher than that in longitudinal vibration. However, the critical cutting depth of brittle-ductile transition in longitudinal vibration is greater than that in Longitudinal-torsional resonance, when the feed speed is increasing. By comparing different scratch conditions, the ultrasonic vibration can effectively improve the critical cutting depth of brittle-ductile transition, increase the machining range of ductile domain, and improve the surface quality of Zirconia Ceramics.