Objective:To investigate possible correlation between nutritional status and forced expiratory volume in 1 second expressed as percent predicted (FEV1%) and serum levels of complement components C3 and C4 in patients with chronic obstructive pulmonary disease (COPD).Method:Body weight,FEV1% and serum levels of C3 and C4 in 27 healthy subjects and 40 stable COPD patients were determined and studied the correlation between them.Results:Body weight and C4 serum level in COPD group were much lower than that health group,while C3 serum level was no significant.A significant and positive correlation was present between FEV1% and decrease of body weight and C4 level(γ=0.517 9,0.527 3,respectively).Morever,there was significant correlation between body weight and C4 level (γ=0.487 3) in patients with COPD.Conclusion:In patents with stable COPD,pulmonary funciton was associated with the decrease of nutritional depletion (ND) and serum level of complement components C4,which was an indicator of showing the severe degree of COPD and prognosis.These results suggest that nutritional supplementation and immunological supporting treatment directly influence the curative effect of COPD.