Background The triglyceride glucose-body mass index (TyG-BMI) is considered to be a reliable surrogate marker of insulin resistance (IR). However, limited evidence exists regarding its association with the severity of coronary artery disease (CAD), particularly in hypertensive patients with different glucose metabolic states, including those with H-type hypertension. This study aimed to investigate the relationship between TyG-BMI and CAD severity across different glucose metabolism conditions. Methods This retrospective cohort study included 1537 hypertensive patients who underwent coronary angiography. The TyG-BMI was categorized into tertiles and analyzed using logistic regression models and restricted cubic spline (RCS) models to assess its association with multi-vessel CAD. Receiver operating characteristic (ROC) curves were used to evaluate the predictive value of TyG-BMI in detecting the severity of CAD in different glucose metabolism states, including normal glucose regulation (NGR), pre-diabetes mellitus (Pre-DM), and diabetes mellitus (DM). The above method has also been applied to populations of H-type hypertension patients. Results The TyG-BMI was significantly associated with the severity of multi-vessel CAD in hypertensive patients (Odds ratio [OR] 1.043, 95% CI 1.032-1.053). In the diabetic subgroup, after adjusting for risk factors, the risk of multi-vessel CAD in the T3 groups was 3.836-fold (95% CI 1.763-8.347; P = 0.001) higher than in the T1 group, with a non-linear dose-response relationship (P for non-linearity = 0.017). In H-type hypertension patients, the TyG-BMI was also significantly correlated with multi-vessel CAD (OR 5.248, 95% CI 1.821-15.126, P = 0.002) in the DM group. The ROC analysis revealed that TyG-BMI had the highest predictive value for multi-vessel CAD in diabetic patients, with an AUC of 0.720 (95% CI 0.661-0.780, P < 0.001). Conclusions The TyG-BMI serves as a robust predictor of CAD severity in hypertensive patients, particularly those with diabetes and H-type hypertension. And the non-linear dose-response relationship between TyG-BMI and multi-vessel CAD in diabetic patients underscores its potential clinical utility. This index could serve as a valuable tool for the early identification of individuals at high risk.