To evaluate the aerodynamic performance and flow field quality of a full-scale test bench for a domestic high-bypass-ratio aero-engine, a computational fluid dynamics (CFD) simulation combined with measurement analysis was conducted. A three-dimensional model of the test bench, comprising an intake tower, silencing devices, a flow straightener, the aero-engine, an ejector duct, and an exhaust tower, was constructed using 3D modelling software. A refined mesh was generated, and the standard k-ε turbulence model with wall functions was employed to handle turbulence and near-wall flow. The flow governing equations were solved using the Semi-Implicit Method for Pressure Linked Equations (SIMPLE), and the distributions of velocity, pressure, and temperature fields, as well as natural convection characteristics, were analyzed. The results show that the ejection coefficient of the test bench reached 1.97, and the velocity non-uniformity at the cross-section 6 m upstream of the engine was 29.05%, which meets the relevant industry standard requirements. The flow straightener reduced the velocity non-uniformity by approximately 51.5%, significantly improving flow uniformity. The total pressure non-uniformity at the engine inlet was only 0.3%, indicating a low level of flow distortion. Under natural convection conditions, the wind speed inside the test bench remained below 2 m / s, and the impact of stack effect was limited. Overall, the test bench exhibits a reasonable aerodynamic design and excellent flow field quality, thus satisfying the ground test requirements for the domestic high-bypass-ratio aero-engine.