Driving Mechanism of Cross-border E-commerce and Digital Border Ports on Three Margins of China’s Agricultural Exports to Vietnam

With the rapid iteration of digital trade technology and the continuous improvement of regional cross-border logistics systems, cross-border e-commerce (CBEC) and digital border ports have become core digital infrastructure driving the high-quality growth of agricultural export trade. As China’s most important neighboring agricultural trade partner and a key node of RCEP regional digital trade cooperation, Vietnam presents typical research value for exploring the digital driving logic of China’s agricultural export marginal growth. Based on the heterogeneous trade marginal theory, this paper decomposes China’s agricultural exports to Vietnam into three margins: extensive margin (product diversification), quantity intensive margin (trade scale expansion), and price intensive margin (export quality upgrading). Using panel data of HS6-digit agricultural product exports from China to Vietnam covering 2015–2024, this study adopts multiple linear regression and hierarchical regression models to systematically explore the independent driving effects of CBEC and digital border ports, as well as their synergistic mechanism on the three export margins. The results indicate that both CBEC and digital border ports significantly and positively promote the three margins of China’s agricultural exports to Vietnam; digital border ports exert a stronger driving effect on the quantity intensive margin, while CBEC has a more prominent incentive effect on the extensive margin and price intensive margin. Hierarchical regression verification shows that digital border ports play a positive moderating role in the impact of CBEC on agricultural export margins, forming a synergistic driving effect of “digital platform empowerment + port infrastructure guarantee”. Heterogeneity analysis confirms that the synergistic driving effect is more significant on labor-intensive and high-value-added agricultural products, while the promotion effect on bulk primary agricultural products is relatively weak. This study clarifies the micro driving mechanism of digital trade infrastructure on agricultural export growth, compensates for the research gap in the marginal heterogeneity of digital-driven cross-border agricultural trade, and provides empirical support and policy references for optimizing China-Vietnam agricultural digital trade layout and promoting the high-quality development of regional agricultural exports under the RCEP framework.