Purpose <p>This meta-analysis seeks to examine the impact of different dosages of N-acetylcysteine (NAC) on pulmonary function in individuals with Chronic Obstructive Pulmonary Disease (COPD) and to clarify the dose-response relationship.</p> Patients and methods <p>Systematic searches were performed in PubMed, the Wanfang Database, Cochrane Library, and China National Knowledge Infrastructure (CNKI) for pertinent randomized controlled trials (RCTs) published from 2000 to 2024. Research examining various dosages of N-acetylcysteine (NAC) for the management of chronic obstructive pulmonary disease (COPD) was incorporated. The methodological quality of the selected literature was evaluated utilizing the Cochrane Risk of Bias tool. This Meta-analysis was performed using RevMan software(version 5.4). The primary outcomes were lung function parameters, including forced expiratory volume in 1&#xa0;s (FEV₁), forced vital capacity (FVC), and the FEV₁/FVC ratio.</p> Results <p>High-dose NAC(≥ 1200&#xa0;mg/d)demonstrated significant improvements in FEV₁,FVC, and the FEV₁/FVC ratio, whereas low-dose NAC(&lt;1200&#xa0;mg/d)showed nonsignificant effects. Substantial heterogeneity was observed for some outcomes. However, the efficacy of the high-dose regimen remained robust following sensitivity analysis.</p> Conclusion <p>The findings of this study provide novel evidence supporting the differential effects of various NAC doses on improving lung function parameters in COPD patients. They suggest that high-dose NAC(≥ 1200&#xa0;mg/d)may represent a preferred dosing strategy for enhancing lung function in COPD.</p> PROSPERO registration number <p> CRD420251154781.</p>