Abstract: To investigate the expression of survivin gene and CK18 in thyroid neoplasms and their significance in pathological diagnosis and lymph nodes micrometastasis. Methods The expression of CK18 and survivin gene were detected by immunohistochemical methods (SP) in 56 cases of thyroid cancer,13 cases of thyroid adenoma and 10 cases of normal thyroid tissue. Results (1) The expression rate of CK18 was 100% in all the three kinds of thyroid tissue.The positive expression rate of survivin in the normal thyroid gland, thyroid adenoma and carcinoma was 0.00%,15.38%and 60.71%respectively.The expression of survivin in thyroid cancer obviously different from those of thyroid adenoma and normal thyroid (P<0.05). (2)The positive rate of CK18 in 94 lymph nodes of 56 cases was 35.11%(33/94). It was significantly higher than the positive rate of HE staining which was 20.21%(19/94), (P<0.05).Fourteen lymph nodes of 7 cases were micro metastasis. (3)The expression rate of CK18 in neoplastic tunia invasion in well differentiated thyroid follicular carcinoma was dramatically higher than that of HE staining. Conclusion CK18 was a sensitive indicator in detection of lymph node micrometastasis and neoplastic tunia invasion in thyroid cancer. The expression of survivin has relevance with the occurrence, development and metastasis of thyroid cancer. They can be used as the objective index in clinical pathological diagnosis. survivin gene may become an ideal target in malignant neoplasms gene therapy.