Objective To investigate the predictive value of white blood cell-to-hematocrit ratio (WBCHR) for in-hospital major adverse cardiovascular events (MACE) after reperfusion therapy in patients with acute ST-segment elevation myocardial infarction (STEMI). Methods A case-control study was conducted to retrospectively select 319 patients with first-time diagnosis of STEMI who underwent percutaneous coronary intervention (PCI). Patients were divided into MACE group (69 cases) and non-MACE group (250 cases) based on the occurrence of MACE during hospitalization. Clinical data, including general information, laboratory test indicators, echocardiography, and coronary angiography results, were compared between the two groups. Univariate and multivariate Logistic regression analyses were performed to explore the risk factors for in-hospital MACE after reperfusion therapy in STEMI patients. Receiver operating characteristic (ROC) curve analysis was conducted to evaluate the predictive value of WBCHR for in-hospital MACE after reperfusion therapy in STEMI patients. Results The levels of fasting blood glucose, uric acid, creatinine, white blood cell count, neutrophil count, high-sensitivity C-reactive protein (hs-CRP), D-dimer, and WBCHR were significantly higher in the MACE group than in the non-MACE group, while red blood cell count, hemoglobin, hematocrit, and left ventricular ejection fraction were lower (P < 0.05). No significant differences were observed in age, gender, smoking history, hypertension history, diabetes history, door-to-wire (D2W) time, total cholesterol, triglycerides, and the number of diseased vessels between the two groups (P>0.05). Multivariate Logistic regression analysis revealed that elevated uric acid levels (OR=1.005; 95%CI, 1.002 to 1.009; P=0.004), decreased hemoglobin concentration (OR=0.964; 95%CI, 0.941 to 0.988; P=0.003), increased hs-CRP levels (OR=1.032; 95%CI, 1.009 to 1.056; P=0.007), and increased WBCHR (OR=1.455; 95%CI, 1.295 to 1.635; P < 0.001) were independent risk factors for in-hospital MACE after reperfusion therapy in STEMI patients. ROC curve analysis showed that the area under the curve of WBCHR for predicting in-hospital MACE after reperfusion therapy in STEMI patients was 0.855 (95%CI, 0.796 to 0.914, P < 0.001), with a sensitivity of 63.8% and a specificity of 99.6%. Conclusion WBCHR is an independent influencing factors of in-hospital MACE after reperfusion therapy in STEMI patients and has a high predictive value for in-hospital MACE in these patients.