The potential impact and threat of the rapidly ageing rural labor force in China on food security warrant close attention.Following the logical thread of“labor force ageing－capital deepening－grain production”，this study analyzes the impact of an aging rural labor force on grain-output using a two-way fixed effects model and an instrumental variable approach，based on county-level panel data in 2000，2010 and 2020.The research finds that rural labor force ageing in China has not led to a decrease in grain production，but has had a positive effect，increasing output.The increase is driven by a dual capital deepening path process，manifested through the substitution of mechanical technology and the emergence of new agricultural management entities.Simply put，during the structural transformation phase characterized by an aging labor force in China，dual capital deepening serves as a fundamental pathway to transform the impact of rural labor force ageing into increased grain production and a food security guarantee.