〔Abstract〕 Objective To explore the risk factors of prognosis in patients with severe community-acquired pneumonia(SCAP) in different age groups. Methods A multi-center and prospective study was conducted at 11 teaching hospitals in China from December 2017 to October 2021. Patients who met the criteria were assigned to the elderly group(≥65 years) and the non-elderly group(18-64 years) to demonstrate the clinical characteristics of SCAP. Patients were divided into survival group and death group according to whether they died in hospital, to determine the risk factors associated with mortality by multivariate logistic regression analysis. Results A total of 170 patients with SCAP were included in the study. The age of SCAP was 20-93(65.75±15.23) years old, and the proportion of SCAP in the elderly was 58.82%(100/170). In-hospital mortality of non-elderly SCAP was 24.3%(17/70), and the in-hospital mortality of elderly SCAP was 28%(28/100). Compared with non-elderly group, patients in elderly group had higher severity score and more complications on admission, but the symptoms of fever and respiratory rate at admission were less obvious. In multivariable logistic regression analysis, the factors significantly associated with in-hospital mortality of non-elderly SCAP were pneumonia severity index(PSI) score(P=0.016,OR=1.022, 95%CI1.004-1.041) and invasive mechanical ventilation(P=0.037,OR=4.543, 95%CI1.092-18.898) on admission, and the risk factors associated with in-hospital mortality in elderly SCAP were sequential organ failure assessment(SOFA) score(P=0.006,OR=1.240, 95%CI1.063-1.446) and combined with coronary artery disease on admission(P=0.037,OR=2.834, 95%CI1.066-7.534). Conclusion In-hospital mortality for SCAP is high. PSI score and invasive mechanical ventilation are risk factors for in-hospital mortality of non-elderly patients with SCAP, and SOFA score and combined with coronary artery disease on admission are risk factors for in-hospital mortality of elderly patients with SCAP.