Abstract: With the continuous advancement of mining into deep mining, significant differences in the in-situ stress field between deep and shallow rock masses have emerged. To investigate the evolution law of the in-situ stress field during deep mining, relevant studies are conducted using the Sishanling Deep Mining Area as the engineering background. By comparing the advantages of hydraulic fracturing and surface stress relief methods, the surface stress relief method is selected for more precise measurement and analysis of the in-situ stress. Through the integrated application of the Mohr-Coulomb model and the strain-softening model in FLAC^3D, numerical simulations are conducted to verify the evolution of the stress field before and after deflection. The results show that the in-situ stress field in the deep rock mass undergoes significant deflection after tunnel excavation, with a notable increase in vertical stress around the surrounding rock. The deflection of the stress field has a profound impact on the rock mass state and stress transfer direction near the tunnel. Considering the characteristic that rock tensile strength is much lower than its compressive strength, targeted reinforcement and support measures can be implemented to enhance the stability of deep rock masses. Moreover, the stress field deflection exerts considerable influence on the sidewalls of the tunnel. Special attention should be given to the state of rock mass within 5 meters of the tunnel sidewalls in deep mining, focusing on changes in vertical and horizontal stress distribution to prevent severe rock mass failure that could threaten safe production.