Abstract: Facility agriculture, as an efficient modern agricultural production mode, is an important means of building a diversified food supply system. Based on panel data from 30 provinces in China from 2014 to 2023, excluding Hong Kong, Macao, Taiwan, and Xizang, this study employs a two-way fixed effects model and a moderation effect model to empirically examine the impact of the development level of facility agriculture on the supply of non-grain food. The results show that: 1) The development level of facility agriculture has a significant positive effect on the supply of non-grain food, and this finding remains robust after a series of endogeneity and robustness tests. From a disaggregated perspective, the strongest promoting effect is observed for fruit and vegetable products, followed by aquatic products, while the effect on livestock products is the weakest. 2) Heterogeneity analysis indicates that the promoting effect of the development level of facility agriculture on non-grain food supply is more pronounced in the central and western regions than in the eastern region, and stronger in non-major grain-producing areas than in major grain-producing areas. 3) Moderation effect analysis shows that agricultural technological progress plays a positive moderating role in the relationship between the development level of facility agriculture and non-grain food supply. Based on these findings, it is recommended to accelerate the upgrading of facility agricultural equipment, strengthen agricultural technological innovation, and implement differentiated development strategies for facility agriculture, in order to support the establishment of a stable and reliable diversified food supply system and better meet residents’ diverse dietary needs.