Objective:To observe the effects of Modified Xiayuxue Decoction combined with acetylcysteine on interstitial pulmonary fibrosis. Methods60 patients with interstitial pulmonary fibrosis were randomly divided into the treatment group and control group,30 cases in each group. The treatment group was treated with Modified Xiayuxue Decoction combined with acetylcysteine,and the control group was treated with acetylcysteine,with a course of 6 months. The TCM syndrome score,pulmonary function indexes,6-minute walk distance,St. Georges respiratory questionnaire(SGRQ)score for life quality evaluation and high resolution CT(HRCT)score were observed and compared.  Results:①Compared with treatment before,the TCM syndrome score and SGRQ score were decreased and 6-minute walk distance was increased in both groups after treatment,with statistical differences(P<0.05).There were statistically significant differences on the TCM syndrome score,SGRQ score and 6-minute walk distance between the two groups after treatment(P<0.05). ②After treatment,the diffusing capacity for carbon monoxide of single breath(DLCO·SB)in the treatment group was increased(P<0.05),but there were no obviously changes of all pulmonary function indexes in the control group(P>0.05). The DLCO·SB in the treatment group was higher than that in the control group after treatment(P<0.05). ③For the comparison between treatment before and after within group or between the two groups after treatment,there was no statistically significant difference on HRCT score.  Conclusion:Modified Xiayuxue Decoction combined with acetylcysteine can be used in the treatment of interstitial pulmonary fibrosis,which can improve the TCM syndrome and alveolar diffusion function of patients,enhance the exercise tolerance and life quality,and prevent the progression of pulmonary fibrosis.