Abstract: Objective Procalcitonin (PCT) is a biomarker of early bacterial infection, and it can reflect severity of infection, and regarded as a prognostic factor.In this study, PCT was used to evaluate the clinical value of serum procalcitonin (PCT) in early diagnosis of acute pancreatitis (AP) and predictive of severity. Methods The enrolled included 41 cases of the severe AP (SAP), 68 cases of mild AP (MAP), and 50 cases of normal controls.The levels of PCT and CRP in each group were dynamically detected respectively at 1st, 3th, 5th and 7th day after admission, and the correlations between these indexes and the severity and progress of AP were analyzed and data were processed by statistical software SPSS17.0. Results The levels of serum PCT and CRP in SAP and MAP patients were significantly higher than those of control group (all P < 0.05).In addition to 1st of serum CRP, the rest of S PCT and CRP levels in patients with SAP group were higher than those in the same period of MAP group (all P < 0.05).The threshold of PCT and CRP in SAP were 2.0μg/L and 120 mg/L, respectively.The sensitivity of the serum PCT and CRP were 82.9% and 70.7%, respectively;the specificity of the serum PCT and CRP were all above 90%.The serum PCT + CRP combined detection of sensitivity enhanced to 92.7% and specificity still above 90%. Conclusion Serum levels of PCT can reflect the severity of acute pancreatitis at the early stage and has an important clinical value.When the levels of PCT and CRP reach the cut-off values of2.0 μg/L and 120 mg/L, serum PCT value is a sensitive and specific serological a diagnostic method for diagnosis of SAP.