Objective To explore the guiding role of serum procalcitonin (PCT) in antibiotic therapy during acute exacerbation of chronic obstructive pulmonary disease (AECOPD). Methods Totally 72 patients with AECOPD were randomly divided into PCT group (n=40) and conventional therapy group(n=32).For patients in PCT group,the use of antibiotics was based on PCT serum levels,antibiotics were stopped when PCT＜0.25 μg/L,while in conventional treatment group,the use of antibiotics was based on clinical symptoms of patients.The main observation indexes included ratio of antibiotic usage,time of antibiotics use,hospital stay,clinical efficacy,aggravating cases and death cases. Results There were no significant difference in clinical efficacy between the two groups(82.5％ vs.75.8％,x2 =0.217,P=0.641),however,the ratio of antibiotics usage in PCT patients was significantly lower than conventional therapy group (47.5％ vs.71.9％,x2 =4.346,P=0.037),average time of antibiotics use and days of hospital stay were shorter in PCT treatment group than conventional therapy group [(6.84±3.27) d vs.(10.22±3.67)d,x2 =3.116,P=0.003; (11.7±5.2) d vs.(20.3±8.7) d,x2 =5.202,P=0.000].There were no difference in double infection incidence (2.5％ vs.18.8％,x2 =3.657,P=0.056),aggravating cases (3 cases vs.4 cases,x2 =0.097,P=0.756) and mortality (2.5％ vs.6.3％,x2 =0.039,P=0.843) between the two groups.Conclusions Serum PCT level may be an appropriate indicator to guide antibiotic therapy in patients with AECOPD in view of its effective decreases of excessive use of antibiotics,double infection opportunities and hospitalization time.