Abstract: OBJECTIVE To analyze the value of serum procalcitonin（PCT） combined with extravascular lung water index（EVLWI） in predicting prognosis of patients with acute respiratory distress syndrome（ARDS） caused by severe community acquired pneumonia（SCAP）, so as to provide research basis for optimizing clinical treatment and prognosis evaluation. METHODS Total of 71 patients with ARDS caused by SCAP hospitalized in Department of Respiratory medicine of Tengzhou Central People’s Hospital from Jan 2017 to Jan 2019 were recruited as the research subjects. According to the prognosis of the patients, they were divided into the death group（death due to ineffective treatment during hospitalization） and the survival group（effective rehabilitation and discharge after hospitalization）. The baseline data as well as the white blood cell（WBC）, blood lactic acid（Lac）, serum creatinine（Scr）, C-reactive protein（CRP） and the serum PCT levels at admission between the patients of the two groups were investigated and compared. After admission, the patients were treated with internal jugular central venous catheterization, whose hemodynamic indicators such as EVLWI were monitored by pulse indicator continuous cardiac output（PiCCO） monitor. RESULTS During hospitalization, 31 patients died due to ineffective treatment, accounting for 43.66%. The oxygenation index（OI） level of the patients in the death group was significantly lower than that in the survival group（P＜0.05）. The serum PCT level and EVLWI level in the patients of the death group were（18.40±5.64） ng/mL and（10.70±2.61） ml/kg respectively, which were significantly higher than those in the survival group（P＜0.05）. Receiver operating characteristic（ROC） curve analysis showed that the area under ROC curve(AUC^ROC) of serum PCT and EVLWI in predicting prognosis of patients with ARDS caused by SCAP were 0.828 and 0.790, respectively（P＜0.05）. When the two indicators were combined, AUC^ROC was increased to 0.960（P＜0.05）, and the sensitivity and specificity were 0.903 and 0.875, respectively. CONCLUSION The serum PCT and EVLWI levels are related to the prognosis of patients with ARDS caused by SCAP. The increase of such two indexes indicates the increased risk of death. Clinicians should pay attention to the infection markers and the monitoring of PiCCO indicators in the early stage of the diseases, and timely take treatment measures to improve the prognosis of patients.