Abstract: Objective To investigate the differential expression of Thl,Th2,Th17 and Treg in peripheral blood of patients with frequent acute exacerbation phenotype of obstructive pulmonary disease（COPD）.Methods A total of 36 patients with frequent acute exacerbation phenotype of COPD,37 patients with infrequent acute exacerbation phenotype COPD,14 healthy subjects were included in this study.The clinical data of each COPD patient was collected and peripheral blood Thl and Th2 were detected by flow cytometry.Levels of Th17 and Treg were analyzed for the expression level of immune cells between different phenotype COPD.Results There was no significant difference in Thl,Th2 and Th17 expression between frequent acute exacerbation phenotype and infrequent acute exacerbation phenotype COPD patients（P＞0.05）,but the Treg ratio was significantly different between the two phynotypes（P＜0.05）.There were significant differences in the number of acute exacerbations and COPD assessment test（CAT） score between the two phenotypes（P＜0.05）.Conclusions In the pathogenesis of frequent acute exacerbation phenotype COPD,Treg-mediated inhibition of inflammatory response may be dominant,and CAT score can be used as one of the indicators to distinguish the frequent acute exacerbation phenotype COPD.