BACKGROUND: Complex percutaneous coronary intervention is associated with higher risk of long-term worse cardiovascular outcomes than noncomplex procedures. Stress hyperglycemia ratio (SHR), a biomarker to reflect relative hyperglycemia, has been shown to predict risk of cardiovascular events in patients with coronary artery disease. However, whether SHR-related cardiovascular risk could be seen in patients who underwent complex percutaneous coronary intervention who are at high risk of cardiovascular events remained undetermined. METHODS: This prospective cohort study consecutively recruited 12 220 patients who underwent complex percutaneous coronary intervention from January 2017 to December 2018 at Fuwai Hospital. Patients were categorized according to baseline SHR tertiles (tertile 1: ≤ 0.765; T2: 0.765-0.879 and T3: > 0.879). The primary end point was cardiovascular events including cardiovascular death, nonfatal myocardial infarction, and nonfatal stroke. RESULTS: During a median 3-year follow-up, 389 cardiovascular events (3.6% of the 10 772 patients who completed follow-up) were recorded. Overall, per 1-unit increase in SHR values was associated with 1.62-fold (95% CI, 1.10-2.38) risk of cardiovascular events after adjusting for confounding factors. Upon stratification by glycemic status, in the fully adjust model, elevated SHR was associated with increased risk of cardiovascular events in diabetic patients (T3 vs. T1; hazard ratio [HR], 1.67 [95% CI, 1.20-2.32]). CONCLUSIONS: We found that elevated SHR levels were associated with increased risk of cardiovascular events at long-term follow-up in patients who underwent complex percutaneous coronary intervention, especially in those with diabetes, suggesting that it could help in risk stratification and prognosis in this population.