ObjectiveTo explore the value of ultrasound-guided core needle biopsy (CNB) in diagnosis of thyroid nodules. MethodsThe clinical data of 347 patients with thyroid nodules who underwent ultrasoundguided CNB were retrospectively analyzed, and the results of CNB pathology were compared with postoperative wax pathology results. ResultsAll patients completed CNB successfully and satisfaction rate for tissue samples was 100%. After CNB, local hematoma occurred in two cases and relieved by conservative therapy. The CNB pathology results of 347 cases of patients were as follows: 117 cases were malignancy, including papillary thyroid cancer in 115 cases, undifferentiated adenocarcinoma in 1 case, and squamous cell carcinoma in 1 case; 230 cases were benign, including thyroiditis in 53 cases, and nodular goiter in 141 cases, adenoma in 16 cases, and nodular goitre coexisting thyroiditis in 20 cases. In 132 cases of patients underwent surgery including 113 cases of malignancy and 19 cases of benign disease, the CNB pathology results in 127 cases were consistent with postoperative wax pathology results and false negative occurred in 5 cases. The diameter of thyroid nodules were not more than 0.5 cm in 4 cases, 0.5-1.0 cm in 59 cases, 1-2 cm in 46 cases, and more than 2 cm in 23 cases, and the accuracy rate of CNB pathology results was 75.0%（3/4）, 98.3%（58/59）, 97.8%（45/46）, and 91.3%（21/23）, respectively, which was the highest in 0.5-2.0 cm. The accuracy, sensibility, specificity, positive predictive value, negative predictive value, failure rate, and misdiagnosis rate of ultrasound-guided CNB for differential diagnosis of thyroid malignant nodules from benign nodules were 96.21% (127/132), 95.76% (113/118), 100% (14/14), 1 (113/113), 0.74 (14/19), 4.24%(5/118), and 0 (0/14), respectively. ConclusionUltrasound-guided CNB has important value on differential diagnosis of thyroid nodules, and important guiding significance on treatment of thyroid diseases.