Objective To assess the value of procalcitonin( PCT) in anti-infective therapy by observing PCT concentration change in therapy. Methods Sixty-eight patients with bacterial infection meet the diagnostic criteria were divided into effective group and invalid group,the PCT level on day 1,day 3,day 5 and day 7 were observed respectively. Results PCT concentrations of two groups showed no sig-nificant difference on day 1. The PCT level of effective group gradually declined and PCT level of invalid group gradually rised with significant difference on day 3,day 5 and day 7(P<0. 05). Conclusion PCT level that is positively correlated with inflammation of infectied patients, which can be used as an effective indicator to optimize antibiotic therapy.