Abstract: A hydraulic fracturing test was conducted on a selected testing hole and seven test sections in the Liangshui tunnel of the Lanzhou-Chongqing railway. The results show that the present stress field of the Liangshui tunnel is dominated by a horizontal stress whose magnitude of stress is extremely high, and the maximum principal stress orientation is N80°W～EW, the same as that of the regional tectonic stress field. Due to the small angle be tween the tunnel axis and the maximum horizontal stress orientation at the testing point, this is a great advantage to the stability of the surrounding rock. Using the practical geological conditions and formation parameters, two largescale 3D computational models were established based on measured geostress values; the gravity stress field and tec tonic stress field wre calculated by ANSYS under four condions regarding the gravity, horizontal compression and shear; a macro extended analysis on the protolith geostress field was carried out by a multiple regression equation. The analysis results show that the horizontal lateral geostress value is between 7.0 and 9.0 MPa, and the horizontal lateral pressure coefficient is between 1.0 and 1.5 in most sections of the Liangshui tunnel.