<p>Fiscal decentralization is a key institutional element for improving the environmental governance system, but whether it can promote haze governance has always been controversial. This study uses a two-way fixed effect model to empirically examine the impact of fiscal decentralization on haze and its channels. The results indicate that the impact of fiscal decentralization on haze shows a U-shaped pattern, with a turning point of 0.783 for the entire sample. The validity of this conclusion has been verified through a series of robustness tests. Fiscal decentralization affects haze through two channels: greening and digitalization, creating a mechanism conflict where greening reduces haze while digitalization exacerbates it. The U-shaped pattern is established in the western region, resource-based cities, non-civilized cities, and non-innovative cities, but the inflection point is earlier. This study strengthens the investigation of emerging factors such as greening and digitalization, especially identifying the potential path of digitization that may exacerbate haze pollution, providing a decision-making reference for improving environmental governance systems in different types of cities around the world.</p>