【Abstract】Objective To analyze the influence of post-intensive care syndrome(PICS) on symptom recovery, functional status and quality of life in elderly patients with severe pneumonia. Methods Using a systematic sampling method, a questionnaire survey was conducted on 155 elderly patients with severe pneumonia who were admitted to the intensive care unit (ICU) and successfully transferred from January 2020 to July 2023. A total of 148 valid questionnaires were collected, with an effective recovery rate of 95.48%. According to whether post-ICU syndrome occurred or not, the patients were divided into PICS group (n=69) and non-PICS group (n=79). The two groups were compared in the duration of clinical symptoms, lung function [forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), and percentage of peak expiratory flow to predicted value (PEF%)], and quality of life [short-form 36-item health status questionnaire (SF-36)] at 4 weeks after ICU transfer. SPSS 24.0 was used for data analysis. According to the data type, t test or Chi-square test was employed for comparison between groups. Multivariate logistic regression analysis was used to evaluate the risk factors of PICS in elderly patients with severe pneumonia. Results There were no statistically significant differences in duration of fever, cough, expectoration and lung rales between the two groups of the patients (all P>0.05). There were significant differences in age, scores on acute physiology and chronic health evaluation Ⅱ (APACHE Ⅱ) on the day of admission to ICU and ICU stay between the two groups (P<0.05 for all). Multivariate logistic regression analysis showed that age >70 years old (OR=2.373,95%CI 1.173-4.800; P<0.05), APACHEⅡ score ≥ 20 points on the day of admission to ICU (OR=3.547,95%CI 2.123-5.925; P<0.05) and ICU stay ≥ 10 d (OR=2.992,95%CI 1.644-5.446; P<0.05) were risk factors of PICS in elderly patients with severe pneumonia (P<0.05). The FEV1, FVC, PEF%, and scores of physical health and mental health on SF-36 in the PICS group were lower than those in the non-PICS group at 4 weeks after ICU transfer (P<0.05 for all). Conclusion PICS can cause a decline in lung function and quality of life of patients with severe pneumonia. Patients with older age, critical illness on admission to ICU and longer ICU stay have a higher risk of PIUS, and it is clinically necessary to formulate targeted prevention and control measures.