<p>Sports mega-events not only exert profound social and economic influence, but also create significant opportunities to better urban haze conditions and promote green development. Based on the spatial difference-in-differences (SDID) model, this paper conducts an empirical analysis of national-level and above comprehensive sports mega-events held in 280 Chinese cities from 2003 to 2021, aiming to explore the impact of sports mega-events on urban haze and their underlying mechanisms. The results indicate that sports mega-events significantly reduce the level of urban haze, and this finding has been verified through various robustness and endogeneity tests. Moreover, the impact exhibits obvious regional heterogeneity and seasonal variation: in non-core cities and medium-sized cities, the haze-reducing impact of sports events is particularly pronounced; events held during the autumn and winter seasons show even stronger effects in reducing urban haze, which mey be related to meteorological conditions such as lower temperatures and weaker air circulation. Mechanism analysis reveals that sports events indirectly contribute to the reduction of haze by enhancing the attention of local governments to environmental issues, revealing their intrinsic role in environmental governance. The results provide important theoretical support and practical guidance for cities seeking to leverage sports mega-events to promote green transformation and sustainable development.</p>