PURPOSE: The Composite Dietary Antioxidant Index (CDAI) is a novel, inclusive measure for evaluating the antioxidant potential of diets. We aim to explore the link between the CDAI and abdominal aortic calcification (AAC) in U.S. adults aged ≥ 40 years. METHODS: This cross-sectional study collected dietary and AAC data for individuals aged ≥ 40 years from the 2013-2014 National Health and Nutrition Examination Survey (NHANES) database. The CDAI was calculated using six dietary antioxidants. AAC was evaluated using a semi-quantitative scoring system known as AAC-24, with an AAC score greater than 6 as severe AAC (SAAC). To examine the association between CDAI and AAC, including SAAC, liner/logistic regression analyses and smooth curve fitting were applied. RESULTS: A total of 2,640 participants were included in this study, and significant decreases in AAC score and SAAC prevalence were observed with ascending CDAI levels (P < 0.01). After adjusting for confounding factors, a clear link was established between the CDAI and both AAC score (β = -0.083, 95% CI -0.144-0.022, P = 0.008) and SAAC (OR = 0.883, 95% CI 0.806-0.968, P = 0.008), respectively. Further smooth curve fitting indicated a negative correlation between CDAI and both AAC score and SAAC. CONCLUSIONS: Dietary antioxidant consumption, as quantified by the CDAI, shows an inverse relationship with AAC risk. Additional longitudinal and intervention studies are essential.