Periodontitis is a chronic multifactorial inflammatory disease with dental plaque accumulation. This study aimed to analyze the association between carbohydrate-to-fiber ratio and periodontitis risk.In this cross-sectional study, the data of 6470 participants aged ≥30 years with available oral health exam data of periodontal status were collected from NHANES 2009-2014. Participants were divided into no & mild periodontitis group (n = 3309) and moderate & severe periodontitis group (n = 3161). The possible correlation between the carbohydrate-to-fiber ratio and the risk of periodontitis was explored via univariate and multivariable logistic regression analyses. Odds ratio (OR) and 95% confidence interval (CI) were applied as the effect size.After adjusting for all the confounding factors, carbohydrate-to-fiber ratio <10.89 (OR = 0.82, 95% CI: 0.69-0.97), carbohydrate-to-fiber ratio of 10.89-14.02 (OR = 0.74, 95% CI: 0.63-0.87), carbohydrate-to-fiber ratio of 14.03-18.47 (OR = 0.83, 95% CI: 0.71-0.97) were correlated with reduced risk of periodontitis. In people aged ≥65 years, carbohydrate-to-fiber ratio of 10.89-14.02 (OR = 0.54, 95% CI: 0.30-0.95) and carbohydrate-to-fiber ratio of 14.03-18.47 (OR = 0.56, 95% CI: 0.37-0.86) were correlated with reduced risk of periodontitis in comparison with carbohydrate-to-fiber ratio ≥18.48 group. The decreased risk of periodontitis was also found in males with carbohydrate-to-fiber ratio of 10.89-14.02 (OR = 0.69, 95% CI: 0.49-0.97) and carbohydrate-to-fiber ratio of 14.03-18.47 (OR = 0.73, 95% CI: 0.56-0.95). In people without diabetes, we found that those with carbohydrate-to-fiber ratio <10.89 (OR = 0.75, 95% CI: 0.61-0.93), carbohydrate-to-fiber ratio of 10.89-14.02 (OR = 0.68, 95% CI: 0.53-0.88) and carbohydrate-to-fiber ratio of 14.03-18.47 (OR = 0.84, 95% CI: 0.70-0.99) were linked with lower risk of periodontitis.Low carbohydrate-to-fiber ratio was associated with decreased risk of periodontitis.