Objective:To investigate the expression of IL-17 in human thyroid papillary carcinoma tissues, and explore the role of IL-17 in the development of papillary thyroid cancer. Methods:Real-time RT-PCR,Western blot,immunohistochemistry assay were used to detect the expression of IL-17 in 60 cases of papillary thyroid carcinoma,10 cases of nodular goiter,and 10 cases of Hashimoto’s disease tissues. Statistics methods were applied to analyze the results. Results:①The level of IL-17 mRNA in papillary thyroid carcinoma tissues was higher than that in nodular goiter tissues,and lower than that in Hashimoto’s disease tissues. While While the level in paraneoplastic tissues was higher than that in the cancerous tissue,P < 0.05;②IL-17 protein in nodular goiter tissues was rarely seen,but expressed in papillary thyroid cancer,higher in adjacent tissues and highest in Hashimoto’s disease tissues by comparing the Western blot’s gray value;③Immunohistochemistry assay showed the expression of IL-17 in papillary thyroid cancer and Hashimoto’s disease tissues,and no expression in nodular goiter tissues. The dyed brown areas in thyroid cancer were mainly located on the edge of the tumor;④Clinical data statistics showed that the expression of IL-17 had no correlation with the patient’s age,sex,tumor numbers,but related with tumor size,lymph node metastasis and TNM staging. Conclusion:The expression of IL-17 increases in papillary thyroid carcinoma tissues. It may be involved in the occurrence and development of thyroid cancer by interacting a variety of cytokines and inflammatory cells.