Objective To evaluate the diagnostic performance of thyroid imaging reporting and data system (TI-RADS)classification and elastography in differentiating benign and malignant thyroid nodules according to size. Methods A total of 222 thyroid nodules (209 cases) with solid or predominantly solid internal contentdiagnosed at pathological findings were enrolled in this study, all the 209 cases underwent surgery in our hospital from Jan.2014 to Jun.2014. The diagnostic performance of TI-RADS classification and elastography in differentiating benign and malignant thyroid nodules according to size nodules were evaluated (for≤1 cm and > 1 cm respectively). Results By using TI-RADS category and elastography, 178 thyroid nodules were diagnosed as malignant nodules, and 44 thyroid nodules were diagnosed as benign nodules. The high predictive factors for malignant thyroid nodules of > 1 cm were irregular shape(OR=6.376), microcalcification(OR=21.525), and capsule invasion(OR=3.852), P < 0.05. The factors for thyroid nodules of≤1 cm were anteroposterior to transverse diameter ratio≥1(OR=3.406), capsule invasion (OR=3.922), and high elastography score(OR=1.606), that suggested the possibility of malignant (P < 0.05). For nodules of > 1 cm, the sensitivity, specificity, accuracy, positive predictive value, negative predictive value, and Youden index of TI-RADS combining with elastography were 98.3%(59/60), 68.6%(24/35), 87.4%(83/95), 84.3%(59/70), 96.0% (24/25), and 66.9% respectively; for nodules of≤1 cm, the sensitivity, specificity, accuracy, positive predictive value, negative predictive value, and Youden index were 98.5%(67/68), 30.5%(18/59), 66.9%(85/127), 62.0%(67/108), 94.7%(18/19), and 29.0% respectively. Conclusion TI-RADS category combined with elastography for diagnosis of thyroid nodules in different size has just a bit differently diagnostic indicators, but that play a high diagnostic performance on the thyroid nodules with maximum diameter > 1 cm.