〔Abstract〕 Objective To explore the predictive value of oxygenation index(P/F) for clinical outcomes in adult community acquired pneumonia(CAP) patients. Methods 493 patients with CAP eligible for inclusion were extracted from AHCCDM, and were divided into survival group(n=405) and death group(n=88) according to whether they survived at discharge; multivariate Logistic regression analysis was used to identify independent risk factors associated with hospitalization death in CAP patients; the trend of changes in oxygenation index(P/F) and hospital mortality risk was evaluated using a restricted cubic spline(RCS) curve. Results Multivariate Logistic regression analysis found that independent risk factors affecting hospitalization death in CAP patients included acute and chronic health scores(Apache II score)(OR=1.11, 95%CI: 1.07-1.15,P=0.02), P/F(OR=1.70, 95%CI:1.03-2.82,P=0.04), and hemoglobin(Hb) and HCO-3concentrationP>0.05, which were not statistically significant; restrictive cubic spline regression analysis found that there was a non-linear response relationship between P/F and hospital mortality(non-linear testP<0.001), and a P/F of 250 mmHg was the cutoff point for the hospital mortality association analysis. P/F<250 mmHg, for every 1 mmHg increased in P/F, the risk of in-hospital mortality was reduced by 1%,HR: 0.99(0.99-1.00),P<0.001. P/F>250 mmHg, there was no association between CAP patients and in-hospital mortality,HR: 1.00(1.00-1.01),P<0.001, indicating that other factors played a dominant role. Conclusion A significantly reduced P/F has a high predictive value for mortality in patients with community-acquired pneumonia.