Procalcionin ( PCT) is a soluble protein liberated into the circulation of patients in response to severe systemic in-fection, in particular by bacterial infection.It is used as the most accurate biomarker for the diagnosis of sepsis.This review briefly de-scribes the induction of PCT, the comparison of PCT and other markers of sepsis, the application of PCT measurement in confirmation or exclusion of diagnosis of sepsis, the assessment of severity and treatment effectiveness of systemic infection, the application of PCT in guiding individual and specific treatment of antibiotics, and the anormaly situation of elevated levels of PCT in patients who do not have sepsis.