Abstract: In response to the problems of unsatisfactory crushing effect, low production efficiency, and large equipment loss in traditional mechanical rock breaking methods in tunnels and underground engineering under hard rock and complex geological conditions, research on water jet assisted impact drilling combined with rock breaking technology is carried out. The research aims to develop a new rock breaking method that can achieve fast and accurate pre-cutting grooves through the synergistic effect of water jet and impact drilling, in order to improve construction efficiency and accuracy. Based on the principles of water jet cutting and impact breaking, a high-pressure water jet cutting system and an impact drilling experimental system are established. Through systematic experimental research, the matching relationship between the key parameters of water jet such as jet pressure, target distance, abrasive parameters and cutting speed and drilling parameters such as impact frequency, single impact energy and impact head diameter, as well as their influence on rock breaking effect are explored. Experimental results have shown that the joint construction method has the advantages of high rock breaking efficiency, good contour accuracy, low equipment loss, and low environmental impact, making it particularly suitable for engineering environments with strict requirements for construction disturbance.