Abstract: Objective To investigate the changes of coagulation function indexes in patients with chronic obstructive pulmonary disease(COPD)and community-acquired pneumonia(CAP). Methods Clinical indexes of 81 COPD patients with CAP were analyzed retrospectively. In addition, the patients(n=135)with acute exacerbation of chronic obstructive pulmonary disease(AECOPD), and those with CAP(n=136)and healthy people(n=136)were selected as the controls. The differences of inflammation indexes and blood gas indexes were compared among groups. Results There were significant differences in white blood cell count, neutrophil count, neutrophil percentage, platelet, prothrombin time(PT), fibrinogen(FIB), thrombin time(TT)and D-Dimer(D-D)among groups(P<0.05 or P<0.01). In the COPD complicated with CAP group, the multiple correlation analysis showed that white blood cell count and neutrophil count were positively correlated with D-D(r=0.362, 0.351, P=0.001, 0.001), arterial oxygen partial pressure ［p(O₂)］ was negatively correlated with D-D(r=-0.267, P=0.017), but neutrophil percentage, pH value, arterial carbon dioxide partial pressure ［p(CO₂)］ were not correlated with D-D(r=0.165, -0.040, 0.105, P=0.162, 0.694, 0.349). White blood cell count and p(O₂)were introduced into the regression equation established on the basis of multiple linear regression analysis, and the result showed - that the effect of white blood cell count on D-D was greater than that of p(O₂). Conclusion Both inflammatory reaction and hypoxia may have effect on coagulation function, and the effect of inflammatory reaction on coagulation function may be greater than that of hypoxia.