Abstract：The result of earthquake mechanism solutions shows that the maximum principal stress axes of the modern tectonic stress field are close upon horizontal and the direction of the maximum principal stress is close to EW in east China；but the result of geostress measurements show that the direction of the maximum horizontal principal stress is close to NS in the Qinling—Bashan Mountain. In order to find the reason，the geostress measurements by AE method and by hydraulic fracturing technique were carried out in the same borehole. The borehole with depth of 600 m was drilled in granite rock mass at Dongjianhkou，Shaanxi Province. From 30 to 596 m，20 valid data of horizontal principal stresses and 25 data of the directions of the fissure by the hydraulic fracturing technique are achieved；from 75 to 599 m，11 data of the maximum principal stresses by AE method are gained. Above 200 m，the data of the hydraulic fracturing technique is consistent with that of AE method at different points in the same depth；but below 200 m，the maximum horizontal stress by the hydraulic fracturing technique is 10 MPa larger than those by AE method. At the same time，the data are larger than those by the hydraulic fracturing technique in its neighbouring region. On the contrary，the data by AE method are consistent with it. The result is that the paleotectonic residual stress exists in granite rock mass below 200 m，and the geostress field is composed of the modern tectonic stress field and the paleotectonic residual stress field. The data by AE method are modern tectonic stress，but the data by the hydraulic fracturing technique are the geostress. The result shows that the paleotectonic residual stress is an important composition of the geostress in the Qinling—Bashan Mountain which is the Mesozoic-Cenozoic orogenic belt.
