ObjectiveTo study the diagnostic significance of modified Alvarado Score System for different types of acute appendicitis. MethodsClinical data of 1 930 cases of acute appendicitis, who underwent appendicectomy in The First Hospital of Yulin from Jan. 2004 to Jan. 2014, were retrospectively collected. Then the diagnostic significance of Modified Alvarado Score System was detected and evaluated by receiver operating characteristic (ROC) curve, and its correlation with postoperative pathological results was calculated. ResultsThe modified Alvarado score of cases in progressive group was higher than that of simplex group (7.5±1.3 vs. 3.6±0.7, P < 0.001). The areas under ROC curve of modified Alvarado Score System was 0.943 (95% CI:0.929-0.958, P < 0.001). The critically diagnostic points of Modified Alvarado Score System for differential diagnosis of simplex acute appendicitis and progressive acute appendicitis was 6 score, with sensitivity of 92.9%, specificity of 86.3%, positive predictive value of 96.9%, negative predictive value of 72.6%, positive likelihood ratio of 6.8, negative likelihood ratio of 0.1, and Youden index of 91.7%. ConclusionThis Modified Alvarado Score System has a certain significance for the type diagnosis of acute appendicitis.