Objective To investigate the changes of proadrenomedullin (pro-ADM) and procalcitonin (PCT) in the elderly patients with severe community-acquired pneumonia (SCAP), and assess their prognostic value. Methods A total of 162 elderly SCAP patients who were admitted in Emergency Department of our hospital from January 2016 to September 2017 were retrospectively enrolled in this study. According to the 28-day survival, they were divided into survival group (n=114) and death group (n=48). The serum pro-ADM and PCT levels in the patients were measured in 1,3 and 7 d after SCAP diagnosis. SPSS statistics 19.0 was used to perform the statistical analysis. Student’[KG-*3]s t test or Chi-square test was employed for comparison between the 2 groups, and repeated measures analysis of variance for intragroup comparison. Receiver operating characteristic (ROC) curve was adopted to analyze the prognostic value of pro-ADM, PCT and combination for SCAP at various time points. Results The CURB-65 score, pneumonia severity index (PSI), and the score of acute physiology and chronic health evaluation Ⅱ (APACHE Ⅱ) were significantly higher in the death group than the survival group (P<0.05). When compared with the survival group, the serum pro-ADM level was significantly higher in the death group on 1st day [(4.66±1.83) vs (3.04±1.31) nmol/L], 3rd day [(5.47±1.96) vs (2.95±1.34) nmol/L] and 7th day [(6.81±2.17) vs (1.53±0.82) nmol/L, all P<0.05], but such diffe-rences of serum PCT level were only found on the 3rd day [(3.28±1.24) vs (1.05±0.53) ng/ml] and 7th day [(5.62±1.83) vs (0.26±0.12) ng/ml,both P<0.05 ]. The serum pro-ADM and PCT levels on the 7th day were obviously higher than those on the 3rd day in the death group [(6.81±2.17) vs (5.47±1.96) nmol/L, (5.62±1.83) vs (3.28±1.24) ng/ml, P<0.05]. The area under ROC curve of combined diagnosis was 0.942(0.883-0.998) for 28-day prognosis in elderly SCAP patients, significantly higher than that by pro-ADM alone (0.892, 0.830-0.951) or by PCT alone (0.857,0.793-0.924). The sensitivity and specificity were 95.2% and 86.4% respectively, suggesting good predictive value. Conclusion The changes in pro-ADM and PCT levels are associated with the severity of the disease and prognosis in elderly patients with SCAP, and combination of serum pro-ADM and PCT levels on the 3rd day shows good predictive value for 28-day prognosis.