Objective: To investigate the correlation and clinical significance of pulmonary function test, 6-minute walk test (6MWT) and chronic obstructive pulmonary disease assessment test (CAT) in patients with acute exacerbation of moderate to severe chronic obstructive pulmonary disease (AECOPD). Methods: Between January 2019 and December 2019, 75 cases who were hospitalized in the Department of Respiratory and Critical Care Medicine, Guangxi Zhuang Autonomous Region People’s Hospital were selected, including moderate and severe AECOPD patients (14 moderate cases, 31 severe cases, 30 extremely severe cases). The results of the pulmonary function test, CAT score, 6MWT, and dyspnea score (BORG score) after 6MWT completion or interruption were faithfully recorded by trained nurses on the afternoon of the second day after admission. Results: The heavier the pulmonary function grade was, the shorter the 6-minute walking distance (6MWD) was, and the lower FEV1% was, and the higher the BORG and CAT levels were, and the higher the interruption rate of 6MWD was. The incidence of extremely severe patients was 93.3%. There was a positive correlation between CAT classification and pulmonary function classification (P<0.01), a negative correlation between CAT classification and 6MWD (P<0.01), and a positive correlation between 6MWD and FEV1% (P<0.01). The ROC curve showed that when 6MWD was less than 234 m, BORG score was higher than 6.5 and CAT was higher than 24, which were the best values for predicting future risks. Conclusion: Combined CAT and 6MWT can comprehensively evaluate the severity of disease, exercise and self-care ability before treatment in hospitalized patients with moderate to severe acute exacerbation of chronic obstructive pulmonary disease, as well as guide the rehabilitation treatment plan.