This paper uses both wind tunnel experiments and numerical simulations to explore the cross-floor dispersion characteristics of air pollutants on high-rise building facades under the coupling effect of solar radiation-induced thermal plumes and horizontal wind, considering different pollution source locations and Richardson numbers (Ri). The results demonstrate that when Ri<1.71, the horizontal wind dominates the flow field structure on the leeward side and the dispersion characteristics. When Ri≥1.71, the thermal plume gradually strengthens and becomes dominant. The pollutant concentration gradually decreases with the increase of floors, but the pollution degree and affecting range of cross-floor dispersion first increase then decrease with the increase of Ri. For indoor pollution sources, maximum dispersion risk occurs at Ri=1.71. For outdoor ground pollution sources on the leeward side, when Ri<1.71, the dispersion risk of air pollutants gradually decreases with the increase of floors. When Ri≥1.71, the dispersion risk of air pollutants is higher in the middle of the building and gradually decreases towards the bottom and upper parts of the building.