Abstract: To investigate the characteristics of the geostress field along the axis of the Longmenshan super-long deep-buried tunnel, a 3D geological model was established using ABAQUS based on engineering geological survey and hydraulic fracturing test data. The nonlinear inversion of the geostress field was performed using the Bayesian regularized neural network, analyzing the impact of active fault zones on the geostress field, and comparing the results with traditional multiple linear regression methods. The results indicate: (1) The principal stress increases approximately linearly with the buried depth, with horizontal tectonic stress dominating( ), and the principal stress along the tunnel route exceeds 20 MPa, with local peaks reaching 64.5 MPa; (2) The geostress value in hard rock sections is very high, indicating a moderate risk of rock bursts; in soft rock sections, the risk of large deformation is significant, and local stress differences lead to the instability of surrounding rock; (3) In the fault zone, the variation rane of geostress is large, the azimuth angle shows deviation, and the surrounding strata exhibit stress relaxation and stress concentration in valleys.