Abstract: Objective To compare the ability of pneumonia severity score(PSI) and CURB-65 scores in assessing the severity and prognosis of elderly community acquired pneumonia(CAP) in the elderly aged 65-79 years and ≥ 80 years. Methods A retrospective study of 98 consecutive inpatients with elderly CAP was performed in the First Affiliated Hospital of Chongqing Medical University from September to October 2018. According to the age of patients, they were divided into low age group(65-79 years old, 54 cases) and high age group(≥ 80 years old, 44 cases). We analyzed the general clinical data, calculated the scores of each case and compared the differences in 28-day mortality among patients with different risk stratification of two rules. We drew the receiver-operating characteristic(ROC) curves of the two scoring systems and compared their area under the curve(AUCs) to evaluate the predictive value of severity. Results The 28-day mortality rate was 13.0% in the lower age group and 15.9% in the high age group. The AUCs of the CURB-65 and PSI scores in the low age group was 0.843(95% CI:0.700-0.987) and 0.775(95% CI:0.618-0.932), respectively. Meanwhile the AUCs of the CURB-65 and PSI scores in the high age group was 0.653(95% CI:0.418-0.887), 0.651(95% CI:0.451-0.850), respectively. Conclusion The predictive efficacy of the two scoring systems for mortality in elderly CAP patients decreases with age. In low age patients, the high specificity of CURB-65 score is helpful for selecting high-risk patients for intensive treatment and monitoring and the scoring system is relatively simple, it is more suitable for clinical. Both scoring systems have shown poor prognostic value in older patients.