Objective To analyze the relationship between the level of serum calcium binding protein S 100A12 and the severity of acute pancreatitis (AP) ,so as to provide a simple and reliable method for judging the severity of AP .Methods A total of 68 pa-tients with AP from January 2015 to January 2016 in Luzhou Hospital of Traditional Chinese Medicine were selected as objects in this study ,and complete the examination after diagnosis ,modified CT severity index (MCTSI) was used to grade the severity ,serum calcium binding protein S100A12were tested and compared in patients with different disease grading .The ROC curve of different se-verity patients were made .Judging the severity of critical value according to the S 100A12 curve inflection point ,basing on the judg-ment of MCTSI ,the sensitivity ,specificity and accuracy of S 100A12 in grading condition of AP were calculated ,then the value of S100A12 was evaluated .Results The level of S100A12 increased with MCTSI grade rising ,there were significant differences in S100A12 level between different grades patients(P<0 .05) .ROC curve analysis showed that the clinical limits of gradeⅠto Ⅲ were 26-80 ,81-260 ,>260 ng/mL respectively .The sensitivities accuracy of S100A12 judging grade Ⅰ ,grade Ⅱ and grade Ⅲ were 88 .89% ,94 .12% ,80 .00% ,the specificity were 75 .00% ,94 .12% ,96 .55% ,the accuracy were 82 .35% ,94 .12% ,94 .12% respec-tively .Conclusion The serum calcium binding protein S100A12 estimates is consistent with MCTSI for judging the severity condi-tion of AP .