Objective:To explore the application value of serum cystatin C(CysC)and gamma-glutamyl transferase(GGT)levels combined with arterial blood gas analysis on evaluating the severity of chronic obstructive pulmonary disease(COPD).Methods:157 COPD patients were selected and divided into mild group(n=78),moderate group(n=49)and severe group(n=30)according to the severity of the disease.Clinical data as well as laboratory indicators at admission were collected.The factors affecting the severity of COPD and their correlation with patients'FEV1%pred were analyzed,and the diagnostic value of these factors on the severity of COPD were analyzed.Results:The levels of serum CysC,GGT and arterial partial pressure of carbon dioxide(PCO2)in the three groups were manifested as severe group>moderate group>mild group(P<0.05)while the arterial partial pressure of oxygen(PO2)and oxygen saturation(SaO2)were represented as severe group