Objective To evaluate the clinical efficacy and safety of modified Weijing Decoction in the treatment of stable stage of bronchiectasis(phlegm heat accumulating in the lung pattern).Methods A series of N-of-1 trials using bronchiectasis patients in stable stage with phlegm heat accumulation in the lung pattern were performed.Participants meeting inclusion criteria underwent two distinct treatment protocols during a therapy period.Modified Weijing Decoction was used in the experimental period and ambroxol tablets were used in the control period,washout periods were set.The medication-use order in the control period and experimental period is random.The visual analog scale(VAS)was used to assess symptom changes before and after treatment.24-hour sputum volume and COPD self-assessment test(CAT)scores were recorded,while adverse reactions were monitored during the study period.Statistical analysis and drawing were performed on SPSS 25.0 and GraphPad Prism 8.Comparison of inter-group differences before grouping was assessed by independent samples t-test.Analysis of symptom score,24-hour sputum volume and CAT scores in the experimental and control periods,as well as comparison of differences between the above two groups before and after treatment were performed using paired t-test,which enabled comprehensive exploration of clinical and statistical distinctions.Results A total of 9 patients participated in 16 rounds of analysis.Statistically significant differences(P＜0.05)before and after the treatment in the experimental period were noted in total Traditional Chinese Medicine(TCM)symptom scores,cough,sputum,sputum color,chest tightness and chest pain,bitter and dry mouth,fatigue and tiredness,24-hour sputum volume,and CAT score.Paired t-tests revealed significant variations(P＜0.05)in the total TCM symptom scores,sputum color scores,scores of chest tightness and pain,and 24-hour sputum volume between experimental and control periods.No adverse events related to the test methods or drugs occurred during the observation period.Conclusion Modified Weijing Decoction could comprehensively improve clinical symptoms of bronchiectasis patients in stable stage.It exhibits superior efficacy compared to ambroxol,and maintains a favorable safety profile.