<p>Unlike symmetric canyons, step-down configurations enhance windward pollutant accumulation, aggravating local air pollution.To address this issue, this study used the computational fluid dynamics (CFD) model, validated through the wind tunnel experiments, to systematically assess the performance of 120^° deflection-angle wind catchers (The direction of the incoming wind is at a 30° angle to the wind-catcher structure) with three different inclination lengths in regulating flow patterns and enhancing vehicle exhaust dispersion within a step-down canyon equipped with green belts or solid walls, under a perpendicular wind condition. Results demonstrate that: (1) the standalone use of solid walls increases the overall pollutant concentration in the canyon by 5.4%, it significantly reduce pollutant levels in health-sensitive areas (e.g., at pedestrian breathing height (PBH) in windward zone, average and maximum pollutant concentrations decreased by 35.6% and 42.9% respectively), while green belts alone are ineffective; (2) wind catchers can significantly intensify the counter-clockwise primary vortex, while eliminating near-ground horizontal flows, leading to substantial reductions in the pollutant concentrations, along with achieving uniform windward-side pollutant distribution along the street axis; and (3) the coupled use of a wind catcher with solid walls provides additional reduction of pollutant concentrations in health-sensitive areas (e.g., under three different wind catcher’s inclination lengths, average and maximum concentrations decreased by 3.5–11.9% and 16.0-22.6% respectively at the windward wall, and by 15.4–24.1% and 15.1–22.0% at PBH in the windward pedestrian area), whereas the wind catcher-green belts system yields no additional benefits. The study highlights the effectiveness of wind catchers, especially when integrated with solid walls, in improving step-down canyon air quality.&#xa0;</p>