Abstract: The stick-slip vibration of PDC bits is one of the main factors leading to abnormal wear of the bit during deep and ultra-deep well drilling. In order to explore the influence mechanism of the composite impact load on the stick-slip vibration of PDC bits, the development law of the stick-slip vibration during the rock breaking process of PDC bits was studied using the impact rock breaking test device. On this basis, the influence of the axial and torsional composite impact load on the stick-slip vibration of PDC bits during rock breaking was analyzed by introducing the composite impact load. The research results show that at a fixed driving rotation speed, the stick-slip vibration of PDC bits will demonstrate an apparent increase as the drilling speed increases. When the average weight on bit (WOB) is 20.12 kN, and the stick-slip ratio is 1.31, with intermittent bit rotation stagnation. The main frequency of the stick-slip vibration is the first-order natural frequency of the torsional loading module of the impact rock breaking test device. The composite impact can significantly reduce the slip-slip phenomenon of PDC bits during rock breaking, which is represented by the significant reduction of the rotation speed amplitude at the main frequency, and the composite impacts of 50 Hz and 100 Hz have the most obvious suppression on stick-slip vibration with the test parameters. The research results can provide guidance for the suppression of stick-slip vibration of PDC bits during rock breaking and the development of composite impact rock breaking tools.