At present PDC drill bits are widely used for deep hole drilling in hard rock, where the phenomenon of stick-slip vibration often happens in the drilling process, causing low drilling efficiency and short bit life-span. In order to solve this problem, a new torsional impactor has been developed, which can not only mitigate stick-slip vibration of the PDC bit by torsional impact, but also cater to high temperature deep hole drilling environment. The turbine set is designed as the power supply for making full use of mud energy with the universal joint and the reducer used for torque transmission; then torsional impact is achieved by rotating of the impact components. According to this design concept, structural design, prototype trial-manufacture, test platform construction and performance test of the torsional impactor have been carried out. The test results show that the design of the torsion impactor is feasible. It provides impact frequency of 4 to 5Hz with the calculated torque per impact at 651.45 to 814.28N ·m, achieving the initial design goals.