Abstract: The next-generation passenger aircraft feature higher cruise speeds, rendering transonic buffet and Reynolds number effects pivotal in their aerodynamic design. This paper employs the high-precision delayed detached eddy simulation, based on the k-ω SST turbulence model, to investigate the aerodynamic characteristics of the CHN-T2 model for wide-body aircraft. Unsteady simulations demonstrate that, for a cruise Mach number of 0.85 and a Reynolds number of Re = 5×10⁷, the critical angle of attack at which the transonic buffet manifests is 4.4°. Large-scale separation around the wing root trailing edge serves as an indicator for the presence of the transonic buffet of CHN-T2, which exhibits the low-frequency (St = 0.0297) shock oscillation and high-frequency (St = 0.314) fluctuations in the high-pressure region near the trailing edge of the wing root. Regarding the Reynolds number effects, as the Reynolds number increases from Re = 5×10⁶ to 5×10⁷, the shock wave position on the CHN-T2 wing shifts aft by approximately 10% of the local chord length, and the boundary layer thickness decreases by 10% to 50%, resulting in considerable variation in the aerodynamic coefficients. It is further revealed that the Reynolds number effect on the lift and friction drag coefficients remains unchanged regardless of the angle of attack, whereas that on the pressure drag coefficient is linearly correlated with the angle of attack. Concurrently, the variation in the Reynolds number significantly affects the unsteady flow field of transonic buffet, with excessively low Reynolds numbers potentially leading to the disappearance of shock wave oscillations. An increase in the Reynolds number will significantly enhance the shock oscillation intensity but barely affect the high-frequency fluctuations at the wing root trailing edge.