Objective To explore the clinical value of serum procalcitonin (PCT)-based antibiotic therapy in the second-classedexacerbations of chronic obstructive pulmonary disease (AECOPD). Methods 240 patients diagnosised as AECOPD were randomized to the PCT group and the control group. Serum PCT levels of patients from the PCT group were measured 1 h after hospitalized and the third, fifth, eighth day respectively. When PCT < 0.1 μg / L, patients will stop taking antibiotics and initiated while PCT≥0.1 μg / L. Antibiotic treatment in the control group was based on guidelines of COPD diagnosis and treatment. Results Duration of antibiotic therapy and hospitalization were respectively 5.6 ± 1.4 and 8.2 ± 1.1 days in the PCT group, 9.2 ± 2.2 and 11.4 ± 2.5 days in the control group (both P < 0.05). Mean costs of hospitalization expensesand antibiotic therapy were 5700 ± 201 and 1650 ± 189) yuan in the PCT group, 6210 ± 220 and 2350 ± 210 yuan in the control group (both P < 0.05). The clinical effective rate, times of exacerbation, one-year ΔFEV1, the 1-year hospitalization rate and time to next exacerbation all showed no significant differences between the two groups. Conclusion PCT-guided antibiotic treatment reduces antibiotic use inthe second-classed acute exacerbations patients.