It is widely accepted that the rock-breaking threshold pressure for rock erosion using the supercritical carbon dioxide (SC-CO2) jet is lower than that for conventional drilling fluid. A combined swirling and straight jet nozzle was designed to incorporate the advantages of the swirling jet and the straight jet. To fully utilize the SC-CO2 and the combined swirling and straight jet, a novel rock-breaking method that uses the combined swirling and straight SC-CO2 jet is presented. Experiments were performed to investigate the influence of important parameters on rock-breaking performance, including the length and center diameter of the impeller, the length of the mixing chamber, the standoff distance, and the jet pressure. The results reveal that this novel rock-breaking method can achieve a large rock erosion volume. As the impeller length, mixing-chamber length, and standoff distance increase, the rock-breaking performance initially improves and then declines, indicating that optimal values exist. An increased center diameter of impeller can result in deeper breaking but reduces rock-breaking diameter. Moreover, the rock-breaking efficiency can be enhanced by increasing the jet pressure. The results of this study can be used as an experimental basis for further research.