In order to solve the problem of huge consumption of traditional water jet rock breaking resources, it is urgent to develop an efficient and energy-saving jet rock breaking technology in order to achieve the purpose of energy conservation, emission reduction and green sustainable development. Based on the computational fluid dynamics method, the quantitative gas phase is added to the water jet to form the gas-liquid two-phase jet, and its numerical simulation is carried out. The characteristics of the velocity field and pressure field of the gas-liquid two-phase jet are studied, and the effects of gas volume fraction, incident pressure and jet distance on the rock breaking performance parameters of the gas-liquid two-phase jet are analyzed. The results show that the maximum axial velocity of gas-liquid two-phase jet with gas volume fraction of 30% is 288 m/s, which is more than 19% higher than that of pure water jet. When the jet is ejected from the nozzle, the high-pressure bubble collapse will form a high-speed collapse micro jet, which will improve the jet velocity and jet impact force. With the increase of gas volume fraction, the maximum axial velocity of jet increases, while the stagnation point pressure decreases slightly. With the increase of incident pressure, the maximum axial velocity of jet increases, but the increase decreases gradually. When the jet distance increases to 35 mm, most of the bubbles in the jet collapse near the target surface and produce pulsating impact on the target surface, so that the stagnation point pressure rises to 26 MPa. At this time, the stagnation point pressure is high, the jet diffusion is small, and the rock breaking performance of the jet is good.