Abstract: The Reynolds number effect presents a critical technical challenge in the design of large aircraft, significantly impacting flight safety, aerodynamic performance, development efficiency, and cost. This paper first introduces the primary research methodologies employed to study Reynolds number effects from the perspective of large aircraft design and development, consisting of wind tunnel testing and numerical simulation. Subsequently, the influence patterns of Reynolds number effects on key aerodynamic components are analyzed, including supercritical airfoils/wings, full-configuration aerodynamic design, low-speed high-lift devices, winglets, and vortex generators. Concurrently, the paper reviews research progress on the flow mechanisms associated with these Reynolds number effects. Furthermore, several potential solutions to address Reynolds number effect challenges are elaborated, encompassing advanced wind tunnel testing techniques, data correction methods, and artificial intelligence technologies. Finally, the paper summarizes existing research achievements and identifies current limitations concerning Reynolds number effects. Based on this assessment, specific recommendations for future research directions are proposed.