<p>Three-dimensional ultrasonic vibration-assisted turning as a representative of non-traditional turning can produce special structures used to improve the surface wetting characteristics of workpiece. In this paper, a novel surface contact angle prediction model was developed based on this technique. The effect of air in surface structure on contact angle was considered in this model. Finally, the model was proved to be positive through experiments. The experimental results show that turning speed and feed rate have a greater effect on the contact angle of workpiece surface than the depth of cut and the amplitude of tool nose. This study is important for enriching the theory of three-dimensional ultrasonic vibration-assisted turning.</p>