[Abstract] Objective: To investigate the ultrasonographic characteristics of medullary thyroid carcinoma (MTC). Methods: A retrospective analysis sonographic features of 40 MTC. For comparison, ultrasound appearances of 60 thyroid papillary carcinoma and 97 benign thyroid nodules were evaluated also.The differences in the lesion number, diameter, boundary, shape, aspect ratio, cystic component, solid partial echo, calcification, blood supply and neck lymph node of MTC and PTC and thyroid benign nodules were compared respectively, and the features of MTC were summarized. Results: The MTC was large, hypoechoic(97.5%), solid（92.5%）,A/T < 1 (97.5%), clear boundary (62.5%), morphological rules (45%), can have calcification (32.5% coarse calcification, 25% microcalcification), blood supply is rich (95%),lymph node metastasis（65％）. Serum calcitonin levels were significantly increased in 7 MTC preoperation. Conclusion: MTC has general ultrasonic characteristics of thyroid malignant tumor, but it is different from common PTC and has its own characteristics. Atypical MTC is easily misdiagnosed as benign thyroid nodule. It can be combined with serum calcitonin detection and cytological biopsy.