Abstract: This paper introduces the principle and method of hydrofracturing insitu stress measurement and its applications in the south-north water diversion project of the western line.The magnitude and direction of the principal stress were measured along the line of the water diversion project and their mutual relation and distribution characteristics were analyzed.The results show that horizontal principal stress is dominant in the present crustal stress field,indicating a reversed fault state.Because the(H_max/σ_V) value is higher,the tectonic activity in the area is intense.The principal compressional stress is generally northeast-directed and intersects with the regional tectonic line at an acute angle.Therefore,it is the main dynamic force for the transpressional sinistral movement of most regional faults.Moreover,the possibility of rock bursts in the deep tunnels is analyzed.These provide reliable data for the prevention and control of hazards in tunnels and the optimized design of various diversion lines for the south-north water diversion project.