Abstract: Objective:To study the value of serum calcium and C reaction protein (CRP) in predicting the severity of acute pancreatitis(AP). Methods:The serum calcium and CRP were monitored on day 1,2,3 and 4 in 52 patients with mild AP(MAP) and 21 patients with severe AP(SAP),their diagnostic value was assessed. Results:The level of serum CRP increased significantly in AP group on the the first day of admission and reached the peak on the second day,which was more obvious in SAP group than in MAP group(P<0.01). The diagnostic sensitivity of CRP was 87.3%,specificity 91.8% and AUC 0.924. No significant difference was found between the MAP group and the normal control(P>0.05),and the levels continued to desend with time goes by. Compared with the normal control group,the level of serum calcium in SAP group decreased notablely on the the first day of admission(P<0.01). The diagnostic sensitivity of serum calcium was 82.4%,specificity 86.1% and AUC 0.876. Conclusions:Serum calcium and CRP can be used as a reliable index in evaluation of the severity of acute pancreatitis.