Because of harmful working conditions such as stick-slip vibration,traditional PDC bits were not adapted to hard formations.But when combined with TorkBuster life and ROP of PDC bits can be improved greatly,and PDC bits are adapted to hard formations.To find causes that stick-slip vibration of PDC bits happens,by mechanical analysis of single cutter tooth,it’s found that the critical WOB and torque increases more and more when arc length of PDC cutting into rock increases or rock formations are from soft to hard,and when the critical WOB(weight on bit) and torque exceeds the output of the drill machine,the PDC bit will stop,and torsion angle of drill string increases continually.Accumulation of energy of the drill string will lead to stick-slip vibration.To find theories that TorkBuster improves working conditions of PDC bits,the transient process of small bit acting on rock is simulated with Ansys soft,and it’s found that torsion angle of drill string reduces obviously and aggressivity of PDC bits to rock increases linearly with the torsional impact.By reducing energy accumulation of drill string and increasing aggressivity of PDC bit to rock stick-slip vibration is reduced basically.