Food security is the foundation of national security, and the Soybean Production Capacity Enhancement Project is a key policy to safeguard China’s food security. Based on the background of China’s Soybean Production Capacity Improvement Project, this article first constructs a computable partial equilibrium model under an open economy, and deeply reveals the internal mechanism of the economic and welfare impact of subsidy policies from the industry level; then, using data on global soybean production, trade, and consumption in 2021, we simulate and analyze the impact of China’s subsidy policy for soybean producer on soybean production, price, trade, producer and consumer surplus, and social net welfare in relevant economies from a global perspective. The simulation results indicate that subsidy policy has the output promotion effect and import substitution effect in China, and the long-term effects are much greater than the short-term effects, thereby reducing import reliance and improving China’s soybean self-sufficiency and supply security, but it does not alter the fundamental structure of global soybean production and trade. Subsidy policy can not only increase the welfare of soybean producers and consumers, but also increase the net social welfare of the world. This study can provide decisionmaking basis for the formulation and implementation of China’s food security policies.