ABSTRACTSevere fever with thrombocytopenia syndrome (SFTS) is an infectious disease caused by a novel bunyavirus that poses a significant threat to human health. The aim of this study was to identify a precise and user‐friendly indicator for predicting the mortality of patients with SFTS. We retrospectively analyzed data from 181 hospitalized patients with SFTS. Inflammatory markers, including the neutrophil‐to‐lymphocyte ratio (NLR), lymphocyte‐to‐monocyte ratio (LMR), platelet‐to‐lymphocyte ratio (PLR), systemic inflammation index (SII), systemic inflammatory response index (SIRI), C‐reactive protein‐to‐albumin ratio (CAR), and inflammatory burden index (IBI), were compared between the survival group and the nonsurvival group. A receiver operating characteristic (ROC) curve was used to evaluate the diagnostic value of the IBI for the poor prognosis of SFTS patients. Survival analysis was performed using the Kaplan‒Meier (KM) method. Univariate and multivariate Cox regression models were used to explore factors influencing the prognosis of hospitalized patients with SFTS. The results indicate that patients with high IBI had significantly higher mortality rates than those with low IBI. ROC curve analysis revealed that the IBI had better predictive value than the other indicators did, with an optimal cutoff value of 0.878. Kaplan–Meier survival analysis revealed that patients with high IBI had higher mortality rates and shorter survival times. Multivariate Cox regression analysis demonstrated that the IBI was an independent risk factor for poor prognosis in patients with SFTS. Therefore, the IBI can be used to help clinicians identify high‐risk individuals and implement timely therapeutic interventions.