Abstract：The following preliminary results are obtained based on in-situ stress measurement in the west route area of South-to-North Water Transfer Project of China by using hydraulic fracturing (HF) method：(1) the largest amplitude of maximum horizontal principal stress in all the boreholes along the water transfer route is about 25 MPa with the orientation of NNE or NEE；(2) the largest amplitude of maximum horizontal principal stress is about 17 MPa in all the boreholes in the dams areas，and the orientations are mainly NNE or NEE though influenced by local topography；(3) the ratio of lateral pressure decreases with the increasing depth in all boreholes along the water transfer route. When the depth is greater than 200 m from the ground surface，the ratio is close to 2；(4) the ratios of lateral pressure in all boreholes are greater than 1，which implies that the tectonic stresses in this area are dominant；(5) the magnitudes of the maximum and minor horizontal principal stresses increase with the increasing depth of boreholes；(6) the fine linear relationship between the magnitude of maximum horizontal principal stress and borehole depth in all boreholes along the water transfer route is observed based on regression analysis；and (7) medium rock burst or rheology is likely to be induced by the high stress in the deeply buried long tunnels.
