In order to reveal the distribution characteristics of the initial in-situ stress field in deep-buried water conveyance tunnels and the evolution of rockburst tendency under excavation disturbance, a deep-buried water conveyance tunnel in the tectonic transition zone of the western Sichuan Plateau was taken as the engineering background. Hydraulic fracturing in-situ stress measurements, finite difference numerical simulation, multiple linear regression inversion, and a global–local multiscale nested numerical analysis method were used to investigate the regional three-dimensional initial in-situ stress field and the rockburst tendency evolution before and after excavation, and to analyze the stress redistribution characteristics of the surrounding rock. The results show that the in-situ stress field in the study area is jointly controlled by gravitational stress and tectonic stress. The stress magnitude generally increases with burial depth, and a high-stress concentration zone forms near the maximum burial depth. The deep-buried basalt tunnel section from K4+600 to K9+370 generally exhibits moderate to strong rockburst tendency, with the most prominent rockburst risk near K7. When the tunnel face approaches and passes the typical monitoring section, the deviatoric stress, elastic strain energy density, and strength–stress ratio of the near-wall surrounding rock change significantly. The haunch is the main rockburst-sensitive area, followed by the spandrel and local arch foot. It is concluded that the evolution of rockburst tendency in deep-buried tunnels is jointly controlled by the initial high in-situ stress and excavation disturbance. The haunch, spandrel, and shallow surrounding rock near the local arch foot should be regarded as key areas for rockburst prevention and control during construction. The results can provide a reference for rockburst risk identification and construction control of deep-buried water conveyance tunnels in complex tectonic regions.