Accurate in-situ stress measurement and refined numerical inversion analysis play an important role in the safe construction and efficient operation of high-head pumped storage power plants. This study focuses on a plant located in Xinjiang under complex geological conditions. A comprehensive in-situ stress measurement campaign is conducted by means of the conventional hydraulic fracturing method, the three-dimensional hydraulic fracturing method, and the aperture deformation method. These measurements are combined with multiple linear regression analysis to achieve the inversion and reconstruction of the in-situ stress field for the analysis of stress distribution characteristics and anti-splitting capacity of the surrounding rock at key locations along the water conveyance tunnel. The results demonstrates strong consistency in stress values and orientations across the three measurement methods at the intersection of the in-situ stress boreholes; this cross-validation can improve the overall accuracy of the measurements. The calculated stress values by the numerical inversion model based on the comprehensive in-situ stress data are consistent with those of the in-situ measurements, demonstrating the model’s reliability for large-scale stress field inversion and reconstruction in the engineering area. The stress distribution along the water conveyance tunnel reveals significant disturbances in the in-situ stress field caused by topography and geological structures, so the stress characteristics of the surrounding rock in the engineering area are mainly σH>σz>σh. The azimuth angle of the maximum horizontal principal stress of the surrounding rock varies between NE40°-65°, aligning closely with the powerhouse axis at approximately NE45°. This alignment indicates a well-chosen location of the powerhouse axis. According to the minimum principal stress criterion, the minimum anti-splitting safety factor at key tunnel locations can reach 1.53, demonstrating sufficient resistance against splitting.