Abstract: Objective To explere effect of protein malnutrition on lung function in patients with chronic obstructive pulmonary disease (COPD).Methods 182 cases of COPD were divided into normal nutritional status group and malnourished group.Their nutritional status, lung function and blood gas were compared.Results Differences were statistically significant in maximal voluntary ventilation (MVV), forced expiratory volume in one second (FEV_1.0), forced vital capacity (FVC), PaO₂, PaCO₂ between the two groups.Conclusion Protein malnutrition has great influence on ventilation of patients with COPD.Early detection and improvement of their nutritional status should be made in clinics.