The association between the triglyceride-glucose (Tyg) index and coronary plaque in patients with coronary heart disease remains unclear. This study aimed to investigate the relationship between Tyg index and coronary plaque under different levels of blood glucose metabolism. This retrospective study included patients with coronary artery disease who underwent coronary angiography and OCT between January 1, 2023 and January 1, 2024, and ultimately collected 232 coronary plaques. All patients were grouped according to the median Tyg index (T1 group 7.71 ≤ TyG index ≤ 9.13; T2 group 9.14 ≤ TyG index ≤ 10.99). The thickness of plaque fiber cap was measured under OCT, and the plaques were divided into vulnerable plaque and non-vulnerable plaque. The status of glucose metabolism is divided into non-diabetic and diabetic. Baseline data analysis showed that there were significant differences in clinical and biological characteristics between the T1 and T2 groups (P < .05). Logistic regression analysis showed that T2 group was significantly associated with vulnerable plaques compared with T1 group (odds ratio [OR]: 2.638; 95% confidence interval [CI] 1.548-4.494; P < .001). The OR of Tyg index was 2.175 (95% CI 1.409-3.357; P < .001). Receiver operating characteristic showed that the area under ROC curve (AUC) was 0.727 (95% CI 0.663-0.792; P < .001), the best cutoff value was 9.23, the sensitivity was 60%, and the specificity was 81%. In diabetic patients, there was a statistically significant correlation between Tyg index and coronary vulnerable plaque (OR: 3.273; 95% CI 1.240-8.636, P < .05). Triglyceride glucose index is a good predictor of coronary vulnerable plaque.Copyright © 2024 the Author(s). Published by Wolters Kluwer Health, Inc.