To reveal the stress-deformation characteristics of the surrounding rock and primary support structure in a layered biased strata tunnel, a field monitoring study was conducted with the Jiabo Station Tunnel of the Huangtong-Baise Railway as the engineering background. A systematic analysis was performed on the distribution and evolution of the primary support convergence, surrounding rock pressure, axial force of rock bolts, and internal forces within the shotcrete lining and steel arches. The in-situ monitoring results indicate that the surrounding rock at the monitored section is classified as hard rock with high uniaxial compressive strength and strong self-supporting capacity. The convergence of the primary support exhibits a pattern characterized by “haunch-dominated deformation with minor movement at the spandrels”, with a maximum cumulative convergence of 13.2 mm, indicating small and stable overall deformation. The surrounding rock pressure is asymmetrically distributed. The pressure on the anti-dip side is greater than that on the dip side, with a maximum pressure difference of 87.5% at the haunches. Spatially, the pressure is highest at the haunches and lowest at the spandrels, with a maximum haunch pressure of 38 kPa. All measured pressures are below the limits specified by the design code. The axial force of the rock bolts evolves through three distinct stages: rapid increase, fluctuating growth, and gradual stabilization. The axial forces in bolts on the anti-dip side are generally greater than those on the dip side, reaching a maximum of 17.18 kN. A general trend was observed where the axial force is greater at the end of the bolt closer to the tunnel interior, indicating it sustained more tensile force induced by rock mass deformation. After increasing the spacing of the steel arches from 0.8 m to 1.0 m, the maximum internal forces in both the shotcrete lining and the steel arches increase slightly but remained well within the safe range. These findings provide a scientific basis for optimizing the support parameters for tunnels constructed in layered biased strata under similar geological conditions.