Abstract: A pulsating torsional impact drilling tool was designed to provide a polycrystalline diamond compact (PDC) bit with a circumferential impact load to suppress the stick-slip vibration of the bit when it drills into hard formations. First, the structural design of the drilling tool was introduced, and its working principle was analyzed. Then, on this basis, mathematical models were established for calculating its impact energy in vertical wells and circumferential torque. Finally, the working characteristics of the drilling tool were analyzed. The analysis results showed that the circumferential torque of the pulsating torsional impact drilling tool increased with the increase in flow rate and decreased with the increase in the diameter of the throttle nozzle. Its impact energy in vertical wells became higher with the increase in the torque and rotation of the drill string; however it declined as the weight on bit (WOB) increased. The performance of the pulsating torsional impact drilling tool prototype was explored through laboratory tests. The test results were positive and indicated that the drilling tool could achieve high-frequency torsional impact, and its operating frequency, circumferential cavity pressure difference, and circumferential torque were all enhanced with the increase in flow rate. The research and test results demonstrate that the pulsating torsional impact drilling tool has an acceptable structural design, which can provide periodic torsional impact loads for PDC bits and suppress the stick-slip vibration.