Abstract: High-quality flow fields in cascade wind tunnels are crucial to evaluate the aerodynamic performance of compressor cascades. This study examines the impact of different inflow conditions on the flow field quality in a planar cascade wind tunnel, utilizing a high-load compressor cascade. A suction scheme tailored to the wind tunnel’s upper end-wall is developed, and its effects on the flow field quality is investigated. The results indicate that the inflow inhomogeneity and inaccuracy of incidence angle persist across the cascade’s operational range. Notably, the measured incidence angles of the cascade passage exceed the assigned values by 2°～3°. The flow field quality deteriorates with increasing cascade load (increasing inlet Mach number and incidence angle). The incidence angle affects the inhomogeneity of the inlet Mach number and flow angle, while the inlet Mach number primarily affects the former. The upper end-wall suction can effectively improve the flow field quality at high incidence angles with appropriate suction pressure amplitudes. Under the critical suction pressure that yields the optimal flow field quality, the upstream flow field homogeneity is restored, and the difference between the measured and assigned incidence angles is reduced to 0.5°～0.9°. Both the two-dimensionality and the periodicity of the total pressure loss of the cascade are improved, but the periodicity of the outlet flow angle of the cascade remains essentially unchanged. This research provides valuable insights into improving flow field quality in cascade wind tunnels, particularly under high-load conditions.