<p>Land use transition is an essential approach to understanding human-land relationships. Understanding the mechanism of urban land transition (ULT) in relation to environmental pollution is vital within the context of China’s urbanization, though relevant research is limited. Therefore, this study expands the framework of ULT’s environmental effects based on land use transition theory and systematically analyzes the impact mechanisms of ULT on environmental pollution by integrating methods from landscape ecology and econometrics. The results indicate that ULT has a significant and robust effect in reducing environmental pollution. The environmental pollution reduction effect of ULT shows increasing marginal returns as urbanization advances through its stages. Mechanism analysis reveals that ULT partially mediates environmental pollution by promoting economic agglomeration, advancing industrial upgrading, and fostering green innovation. The findings suggest that the pollution-reducing effects of ULT should be integrated into the refinement of policy and market mechanisms, tailored to regional characteristics and stages of urbanization, to achieve regional-level Pareto optimality in land resource allocation.</p>