Abstract: ob＜x＞jectIVE To compare the clinical efficacy and safety of N-acetylcysteine combined with different doses of azithromycin in the treatment of stably COPD. METHODS The data of patients with stable COPD treated with routine therapy and N-acetylcysteine combined with azithromycin were divided retrospectively into control group (40 cases) and observation group (96 cases). The patients in the observation group were treated with N-acetylcysteine combined with azithromycin ba＜x＞sed on conventional treatment. According to the dosage of azithromycin, the observation group was divided into three groups: group A (28 cases, 0.5g / d), group B (39 cases, 0.25g /d) and group C (29 cases, 0.125g /d). All group had a course of 6 months. the pulmonary function indexes, related serum inflammatory factors and the times of acute COPD attack were compared before and after treatment in four groups, and the side effects of each group during the treatment were compared. RESULTS Before the drug treatment, there was no significant difference in lung function, serum inflammatory factors and the number of COPD acute attack among the four groups (P>0.05); After the treatment, the pulmonary function indexes, serum inflammatory factors in all groups were significantly improved(P<0.05) than before; and the improvement degree of the observation group was significantly better than that of the control group (P<0.05). In the observation group, group A and group B were better than group C (P<0.05). In the comparison of the times of acute attack of COPD, the number of COPD in the four groups after treatment was significantly less than that before treatment, but there was no significant difference between the four groups(P>0.05). CONCLUSION In drug therapy for stable COPD patients, N-acetylcysteine combined with azithromycin is used and the azithromycin dosage is 0.25g/d. It has good clinical effect and safety, and it is worth popularizing.