Abstract: Objective To investigate the intestinal mucosal function and the correlation between intestinal mucosal function and clinical indexes in elderly patients with acute exacerbation of moderate-to-severe chronic obstructive pulmonary disease （AECOPD）. Methods A total of 200 elderly patients with AECOPD were recruited in the study group, and 150 age- and sex-matched elderly patients with stable moderate and severe COPD were assigned into the control group. The clinical pulmonary infection score （CPIS） was assessed in the study group. The nutritional status was evaluated between two groups. Blood samples of all patients were collected for testing. The intestinal fatty acid binding protein （I-FBAP）, D-lactic acid, brain natriuretic peptide （BNP） and blood gas indexes were detected and compared between two groups. The correlation between I-FBAP, D-lactic acid, CPIS, BNP and blood gas indexes was analyzed. Results In the study group, the contents of I-FBAP, plasma D-lactic acid, BNP and PaCO₂, and the incidence rate of malnutrition were significantly higher （all P < 0.05）, whereas pH and PaO₂ were significantly lower （both P < 0.001） than those in the control group. In the study group, I-FBAP and D-lactic acid were negatively correlated with PaO₂ （both P < 0.05）, whereas positively associated with malnutrition, CPIS and BNP （all P < 0.001）. D-lactic acid and I-FBAP were not correlated with pH and PaCO₂ （all P > 0.05）. Conclusion Elderly patients with moderate-to-severe AECOPD are complicated with intestinal mucosal damage. The indexes of intestinal mucosal damage including D-lactic acid and I-FBAP are intimately associated with the severity of AECOPD, which can be used to evaluate the severity of AECOPD in clinical practice.