Abstract: Objective To evaluate the relationship between follicular carcinoma of thyroid in different risk group and lymph node micrometastases. Methods The keratin-19 of negative neck lymph nodes in 83 cases in routine pathological examination, was detected by SP immunohistochemistry using keratin-19 monoclonal antibody to confirm lymph node micrometastasis. All of cases were divided into high risk group,middle risk group and low risk group according to factors related to prognosis. The relationship between lymph node micrometastasis and different risk group combined Follow-up visit documents was analyzed. Results Fifty eight neck lymph nodes in 16 cases of all 83 cases(19.3%) showed positive lymph node micrometastasis, and incidence of lymph node micrometastasis was 4/39 in low risk group, 5/32 in middle risk group and 7/12 in high risk group respectively. It showed remarkable difference during 3 groups (P＜0.001).Nine patients in 16 cases with positive lymph node micrometastasis showed local recurrence and distant organ metastasis, in contrast 6 patients in 67 cases with negative lymph node micrometastasis showed same result (P＜0.001). Conclusion Lymph node micrometastasis in follicular carcinoma of thyroid closely correlate to factors related to prognosis.The detection of lymph node micrometastasis can direct assistant postoperative treatment and prognosis evaluation to some extent for follicular carcinoma of thyroid.