Improving agricultural green development (AGD) has become an urgent choice for developing countries to achieve sustainable development and ensure food security. High standard farmland construction (HSFC) has improved agricultural production conditions and ecological environment through artificial improvement of farmland facilities. This study aims to evaluate the role of high standard farmland construction policy in improving agricultural green development. Based on data of rural areas in Hunan, China, this study explores quantitative impacts of HSFC on AGD by differencein- difference model. The results are as follows: (1) The policy will significantly promote the AGD, and the results remain significant after a series of robustness tests, such as PSM-DID. (2) Mechanism analysis indicates that policies primarily promote AGD through two paths: promoting agricultural socialized services and land-scale management. (3) The results of the heterogeneity analysis indicate that differences in the driving effects of policies are present at different levels of AGD, and the policy effect is stronger in areas with high farmer income levels, large per capita arable land, and in non-grainproducing areas than in other areas. The conclusions of this study provide new empirical evidence and implementation path for developing countries to promote agricultural green development.