Abstract: Objective To study the accuracy and clinical signifcance of ultrasonography in diagnosis of lymphatic metastasis of papillary thyroid carcinoma (PTC) in regions Ⅲ, Ⅳ and Ⅵ. Methods Lymphatic metastases in 185 patients with PTC in regions Ⅲ, Ⅳ and Ⅵ who underwent ultrasonography and bilateral clearance of lymph nodes in our hospital from February 14, 2012 to April 22, 2013 were retrospective analyzed. The patients were divided into group A and group B according to their positive or negative cervical lymph nodes. Each group was further divided into A1 and B1 ≤ 0.5 cm group, A2＞ 0.5 cm and B2≤1.0 cm group, A3 and B3＞ 1.0 cm group according to their tumor diameter and into A11, A12, B11, B12, A21, A22, B21, B22, A31, A32, B31 and B32 groups according to the number of lymph nodes in regions Ⅲ, Ⅳand Ⅵ.Lymphatic metastasis of A11 and B11, A12 and B12, A21 and B21, A22 and B22, A31 and B31, A32 and B32 was analyzed after operation. Results Lymphatic metastasis was found in group A (n=83), group B (n=102), group A1 (n=21), group A2 (n=28), group A3 (n=34), group B1 (n=27), group B2(n=23), group B3 (n=52). Positive A11, A12, A21, A22, A31, A32, B11, B12, B21, B22, B31 and B32 were detected in 6, 8, 9, 8, 18, 23, 1, 2, 1, 11, 23 and 39 patients, respectively, and were signifcantly different from positive B11, A12 and B12, A21 and B21. Conclusion Cervical lymphatic metastasis of papillary thyroid carcinoma can occur whether preoperative ultrasonography shows positive cervical lymph nodes. When the maximum diameter of PTC is ≤0.5 cm, ultrasonography can show its lymphatic metastasis in regions Ⅲ, Ⅳ and Ⅵ. When the maximum diameter of PTC is＞ 0.5 cm and ≤ 1.0 cm, ultrasonography can display its lymphatic metastasis in region Ⅵ. When the maximum diameter of PTC is＞ 1.0 cm, ultrasonography cannot reveal its lymphatic metastasis in regions Ⅲ, Ⅳ and Ⅵ.