Abstract: Against the backdrop of the deep integration of the digital economy and high-quality agricultural development, China's National Big Data Comprehensive Pilot Zones have become an important policy vehicle for advancing the digital economy. However, whether this policy can effectively improve the level of high-quality agricultural development, and whether its effects exhibit spatial spillovers and regional heterogeneity, remain to be further examined. Using panel data for 31 provincial-level administrative regions in China from 2011 to 2023, this study treats the establishment of the National Big Data Comprehensive Pilot Zones as a quasi-natural experiment and employs a staggered difference-in-differences model to evaluate the impact of digital economy policies on high-quality agricultural development. The robustness of the findings is further examined through propensity score matching difference-in-differences, synthetic difference-in-differences, placebo tests, and other robustness checks. A spatial Durbin model and heterogeneity analysis across grain-producing functional regions are then used to investigate the spatial effects and regional differences of the policy. The results show that: (1) digital economy policies significantly promote high-quality agricultural development, and the policy effects exhibit a certain degree of lag and accumulation; (2) digital economy policies exert a significant positive direct effect on high-quality agricultural development in local regions, but generate negative spatial spillover effects on other regions, displaying a spatial pattern of "local promotion and external inhibition"; and (3) the promotional effects of digital economy policies vary across grain-producing functional regions, with relatively stronger estimated effects in non-major grain-producing regions. Accordingly, efforts should be made to continuously improve agricultural digital infrastructure and data application systems, strengthen interregional digital resource sharing and policy coordination, and implement differentiated support policies in accordance with regional resource endowments, industrial foundations, and capacities to absorb digital technologies, thereby enhancing the overall effectiveness of digital economy policies in promoting high-quality agricultural development.