Objective:To compare and analyze the clinical diagnostic values of five thyroid nodule malignant risk stratification guidelines.Methods:From October 2019 to October 2021, 926 cases of patients with 1 027 thyroid nodules were recruited in the Second Affiliated Hospital of Xi ′an Jiaotong University. All nodules were categorized individually according to 2015 American Thyroid Association for Ultrasound Malignancy Risk Stratification of Thyroid Nodules in Adults Guidelines(ATA guidelines), 2016 the Korean Society of Radiology and the Korean Society of Thyroid Radiology Thyroid Imaging Reporting and Data Systems(K-TIRADS), 2017 European Thyroid Association Thyroid Imaging Reporting and Data Systems(Eu-TIRADS), 2017 American College of Radiology Thyroid Imaging Reporting and Data Systems (ACR TI-RADS), and 2020 Chinese Thyroid Imaging Reporting and Data System (C-TIRADS). The pathological results were taken as the gold standard, the malignancy ratio of nodules of different categories in each system was calculated. ROC curves were plotted to evaluate the diagnostic efficiencies of different systems, and DeLong test was used to compare the areas under ROC curves. The sensitivity and specificity of different systems were calculated when the maximum point of the Youden index was the optimal cut-off value.Results:In the same stratified system, there were statistically significant differences in the malignant proportion of nodules of different grades ( P<0.05). The malignant proportion of nodules in the high-risk group showed no significant difference among different stratified systems ( P>0.05). Except for C-TIRADS, the malignant proportion of nodules was increased with the increase of diagnostic grade at each grade of the other four stratification systems. ROC curve showed that AUCs of ATA guidelines, K-TIRADS, EU-TIRADS, ACR TI-RADS and C-TIRADS were 0.814, 0.819, 0.814, 0.820 and 0.802, respectively, there was no statistical significance in AUC of different stratification systems (all P>0.05). The optimal truncation values in differentiating benign and malignant nodules were middle-risk malignant nodules, moderately suspicious malignant nodules, middle-risk malignant nodules, class 4 and class 4B. The diagnostic of five stratification systems showed that ATA guidelines had the highest sensitivity (0.784), C-TIRADS had the highest specificity (0.854). Conclusions:The five stratified systems have similar efficacy in differentiating benign and malignant thyroid nodules, and all of them have good diagnostic value.