Abstract: Based on the reality of torsion impact drilling engineering, this paper established a numerical model of single-tooth rock breaking of PDC bit by considering the dynamic parameters of rock RHT material constitutive model and then analyzed the influences of impact load, impact frequency and time parameter on tooth penetration depth in the process of torsion impact. It is indicated that compared with the indoors physical experiment results of single tooth cutting, it is better accordant in the rock cutting morphology. Compared with conventional drilling, the tooth penetration depth of torsion impact is 25.0% greater and its cutting particles are smaller, which is beneficial to the reduction of stick-slip oscillation and the increase of rate of penetration (ROP). As the dynamic load peak of torsion impact increases continuously, the bit penetration depth increases firstly and then decreases. When the ratio of torsion impact load to axial static load is 1.0, the tooth penetration depth is optimal. When the torsion impact frequency is 40-100 Hz, with the continuous increase of impact frequency, tooth penetration depth decreases continuously, but cutting particle diameter gets smaller and smaller. The research results provide an effective reference for the optimization of engineering parameters during the application of torsion impact drilling tool in hard strata.