Extensive research has validated the triglyceride-glucose (TyG) index as a reliable biomarker for cardiovascular risk stratification in elderly populations. However, comparative analyses across diverse ethnic groups remain scarce, with existing literature predominantly focused on homogeneous cohorts. This cross-national study investigates the association between TyG index and coronary heart disease(CHD) incidence in Chinese and British populations, aiming to quantify regional differences in CHD prevalence, and elucidate the TyG index's predictive value for CHD pathogenesis across distinct demographic contexts. Sociodemographic, clinical, anthropometric, and laboratory data were retrospectively collected from the China Health and Retirement Longitudinal Study (CHARLS) and the English Longitudinal Study of Ageing (ELSA). The TyG index was calculated using the formula: TyG = [TG (mg/dl) × FBG (mg/dl)/2]. TyG-BMI and TyG-WC were derived by multiplying the TyG index with body mass index (BMI) and waist circumference (WC), respectively. Logistic regression was employed to assess the relationship between TyG index quartiles and CHD incidence, with the lowest quartile serving as the reference. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. Restricted cubic spline (RCS) regression analyses were performed to evaluate the association between TyG index and CHD. Additionally, the subgroup analysis and interaction of CHD and TyG index in China and United Kingdom (UK) were also analyzed. The CHARLS cohort included individuals aged ≥ 45 years, while ELSA enrolled participants aged ≥ 50 years. A significant disparity in CHD prevalence was observed: 37.84% (910/2405) in CHARLS versus 24.13% (733/3038) in ELSA (p < 0.001). Gender distributions were balanced in both cohorts. Participants with CHD exhibited significantly higher TyG index values and inflammatory marker levels compared to non-CHD groups (p < 0.001). After controlling for confounding variables, regression analysis suggested that the highest TyG quartile (Q4) in China showed a 2.11-fold increased CHD risk (95% CI: 1.51-2.89), whereas the UK cohort exhibited a weaker association (OR = 1.36, 95% CI: 1.08-1.70). A dose-response relationship was observed, with TyG thresholds of 9.72 (China) and 8.51 (UK). Dose-response analyses identified population-specific TyG thresholds for CHD risk escalation-9.72 in China versus 8.51 in UK (p < 0.05). Subgroup analyses further highlighted ethnic heterogeneity: non-diabetic Chinese individuals faced disproportionately elevated risks (OR = 2.41), contrasting with uniform trends in the UK. These findings underscore the necessity of population-tailored cardiovascular risk stratification strategies. Elevated TyG index demonstrates a significant association with increased CHD risk. The observed higher CHD prevalence in China compared to the UK underscores the clinical utility of TyG index assessment for early cardiovascular risk stratification. Future investigations should prioritize multi-ethnic validation studies and explore its potential as a biomarker for precision prevention strategies.