Objective To investigate the value of urea nitrogen to creatinine ratio(UCR)and blood lactate clearance rate(LCR)in predicting the mortality risk of elderly with severe pneumonia.Methods A total of 83 elderly patients with severe pneumonia who were admitted to the respiratory intensive care unit(RICU)of Lai'an Branch of Nanjing Drum Tower Hospital from May 2018 to March 2022 were enrolled in this study.The patients were divided into survival group(n=22)and death group(n=61)according to the prognosis on the 28th day after admission.The risk factors of death in elderly severe pneumonia were analyzed.The predictive value of UCR,LCR and the combination of them at 6 h after admission for the mortality risk of elderly patients with severe pneumonia was investigated.Results The Acute Physiology and Chronic Health Evaluation Ⅱ(APACHE Ⅱ)score on admission,age,the proportion of patients with pneumonia severity index(PSI)grade＞3 on admission,high-sensitivity C-reactive protein(hs-CRP)at 6 h after admission,neutrophil-to-lymphocyte ratio(NLR),red cell distribution width(RDW),white blood cell count(WBC),and UCR in the death group were higher than those in the survival group(P＜0.05).The LCR at 6 h after admission in the death group was lower than that in the survival group(P＜0.05).PSI grade＞3 at admission,UCR increasing at 6 h after admission,and LCR decreasing at 6 h after admission were the risk factors for death in elderly patients with severe pneumonia(P＜0.05).The area under the curve(AUC)values of UCR and LCR at 6 h after admission and their combination for the prediction of death in elderly patients with severe pneumonia were 0.715,0.701 and 0.805,respectively(P＜0.05).Conclusion PSI grade＞3 at admission,UCR increasing at 6 after admission,and LCR decreasing at 6 h after admission are risk factors for death in elderly patients with severe pneumonia.UCR and LCR at 6 h after admission can be used for predicting the mortality risk of elderly patients with severe pneumonia,and the combination of UCR and LCR has higher predictive value.