From the perspective of fiscal-financial policy coordination, this study select A-share listed companies in Shanghai and Shenzhen from 2009 to 2022 as the research sample, employs a double machine learning model to examine the governance effect of green loan interest subsidy policies on corporate ESG greenwashing. The results show that green loan interest subsidy policies significantly curb corporate ESG greenwashing, and this conclusion remains valid after a series of robustness tests. Channel tests indicate that the policy reduces ESG greenwashing by alleviating corporate financing constraints and stimulating green innovation. Heterogeneity analysis shows that the policy effect is more pronounced among firms with stronger internal governance capacity and a better external information environment, and is also stronger in non-heavily polluting industries and regions with higher fiscal autonomy. The findings provide empirical evidence and policy implications for using fiscal-financial policy coordination to curb corporate greenwashing and improve the corporate ESG governance system.