Abstract: Objective To explore the significance of serum endotoxin,allergic C-reactive protein (hs-CRP) and calcitonin original (PCT) in the evaluation of disease condition in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD).Methods A total of 50 patients with AECOPD were selected and conducted with bacterial endotoxin examination,etiology examination and APACHE Ⅱ score evaluation.According to the bacterial endotoxin levels,the patients were divided into endotoxin negative group (n =10) and the positive group (n =40).Patients with difference APACHE Ⅱ score,hs-CRP and calcitonin original (PCT) levels were compared.Results In the 50 cases,there were 40 cases with positive endotoxin expression (80.0％).Phlegm and blood bacteria culture were positive in 9 cases (18.0％),including 1 case with pseudomonas aeruginosa,2 cases with staphylococcus aureus,2 cases with acinetobacter baumannii,4 cases with eosinophilic malt narrow of bacterium.There were significant differences of APACHE Ⅱ score in patients with different levels of endotoxin (P ＜ 0.05).In the endotoxin positive group,hs-CRP and PCT were significantly higher than the negative group (P ＜ 0.05).In the endotoxin positive group,serum hs-CRP and PCT in severe patients were significantly higher than those of mild group (P ＜0.05).Pearson correlation test showed that serum hs-CRP was positively correlated with APACHE scorein patients with AECOPD (P ＜ 0.05).Conclusion In patients with AECOPD,serum endotoxin,hs-CRPand PCT increase significantly,and these indexes can be used as the serum markers for severity of symptoms.