Confronted with the expansion of local governments’ implicit debt and the associated risks induced by the practice of “land-based financing”, substantial alterations occurred in China’s land reserve financing policy during 2016–2017. These modifications led to an entire cessation of land reserve loans and the initiation of specialized bonds designated solely for land reserves. Empirical evidence, gathered through the approximate application of the difference-in-differences method, reveals that the reform of the land reserve financing policy can markedly reduce local governments’ implicit debt level. Based upon this foundation, the results of the triple-difference regression demonstrate that the diminution effect of the land reserve financing policy reform on local governments’ implicit debt is more pronounced in regions characterized by lower levels of marketization and more substantial legal financing constraints. This research enriches the comprehensive understanding of the impact of land reserve financing policy reform, possessing considerable referential value for the prevention and resolution of local governments’ implicit debt.